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JAMES CHESTERMAN & CQ 
BOW WORKS 



MAKERS OF MEASURING TAPES, RULES, 
GAUGES, STRAIGHT EDGES, TRY SQUARES, 



ETC. 



VERNIER SLIDE GAUGE 




TEEL MEASURING TAPE 



ENGINEERS' TRY SQUARE 



ORKSHOP GAUGES AND 
EASURING APPLIANCES 



AN INTRODUCTORY TREATISE ON THE 
RINCIPAL MEASUREMENTS REQUIRED AND THE 
INSTRUMENTS USED IN WORKSHOP PRACTICE 

FOR APPRENTICES AND STUDENTS 



BY 

LOUIS BURN 

A.M.I.HEOH.B., A.M.I.E.E. 




LONDON 

SIR ISAAC PITMAN & SONS, LTD. 
PARKER STREET, KINGSWAY, W.C.2 

BATH, MELBOURNE, TOBONTO, NEW YOBK 
1024 



o f 
S { 



'/ 



INSTITUTE OF SCIENCE, 
Bangalore. 



PRINTED IN GREAT BRITAIN 
AT THB PITMAN PRBSS, BATH 




PREFACE 

THE introduction of machinery, to supplement or 
replace manual labour, is one of the great romances 
of the nineteenth century ; and the consequent 
enormous expansion of trade and commerce is very 
aptly termed the Industrial Revolution. Labour 
resisted rts introduction m the first instance, due 
to an entire misconception as to the true place of 
machinery in a world ever seeking to develop its 
trade and commerce, but to-day industry is little 
hampered by the antagonism of labour as regards 
mechanical contrivances. The mechanic of to-day 
looks upon machinery as a means of adding materi- 
ally to his wage-earning capacity and as an appliance 
creating a demand for labour, whereas originally 
he 'regarded the machine as an invention which 
would reduce the demand for, and the value of 
lab.our in the world's markets. 

The. great development in the use and application 
of machinery led rapidly to a demand for repetition 
work, both as regards the duplication of standard 
forms of machines and also for the production of 
spare parts and replacements for such machines. 
A demand for the rapid production of interchange- 
able parts could only be met by the introduction of 
methods whereby error was reduced to the extreme 
limit of possibility and machine work in engineering 
workshops became in consequence a matter of 
great precision in measurement. To-day, the general 



IV PREFACE 

standard of accuracy has reached a very high level 
of excellence, and in modern workshops the degree 
of precision expected as a matter of routine is as 
high as that which was formerly attained by an 
exceptionally skilled man engaged on the highest 
grade of work. 

The degree of precision now obtainable in the 
work of the mechanic of average efficiency is largely 
the outcome of progress in the development of work- 
shop gauges and measuring appliances, both as 
regards the construction of the machine tool by 
means of which he carries out his work, and in his 
gauging and checking of the work turned out by 
the machine. Apart from the various types of 
purely automatic machines, such as are found in 
all modern engineering shops engaged on repetition 
work, the machine tool of the present day is con- 
trolled as regards extent and variation of work, by 
the mechanic in charge of it. The precision of the 
work is dependent on the accuracy of the measuring 
tools and appliances at his command and on his 
skill in using them. The enormous importance of 
a thorough understanding of such appliances and 
the correct methods of using them will therefore 
be readily understood, and it is believed that this 
small volume will afford a useful introduction to 
the subject. 

LOUIS BURN. 




CONTENTS 



i"AOH 



PAQB 

ill 



CHAPTER I 

DARD UNITS OF MEASUREMENT . . 1 

Unear measurements The standard yard Divisions of the 
rard Fractions and decimal subdivision The metre 
ieasurement by comparison Generation of length standards 
Angular measurement Units of mass Calculation of 
veight 

CHAPTER n 

jE MEASUREMENT .... 27 

Extent of surface Volumetric capacity Parallax Linear 
intensions The rule Graduation of rules Gear cutting 
ules Metric rules Metric and British rules Shrinkage 
ules Precautions with shrinkage rules Steel tapes The 
ernier Combination end measuring bars 

CHAPTER III 

1EOT MEASUREMENT .... 46 

alipers Slide calipers Inside and outside calipers Spring 
ollpers Screw adjusting calipers Hermaphrodite calipers 
nslde calipers Thread or screw pitch gauges Wire Gauges 
'hlckness or feeler gauges Ping and ring gauges Limit 
luges Adjustable callper gauges Depth gauges Hole and 
jep gauges Slip and block gauges 

CHAPTER IV 

)MBTERS ...... 85 

Jorometer calipers Supplementary fittings Direct reading 
ilcrometer Quick adjustment Ratchet stop Compensa- 
on for wear Heavy micrometer calipers Special forms of 
ilcrometer calipers 

CHAPTER V 

ING OFF ...... 102 

irfaoe plates Scrlbers and scribing blocks Straight edges 
it or try squares Combination sauares Bevel protractors 



Vi CONTENTS 

CHAPTER VI 

PAGE 

SELECTION AND OABE OF INSTRUMENTS . 119 

Selection Care of tools Periodic teats for accuracy Rules 
Steel tapes Calipers Micrometer calipers Wire gauges 
General 

CHAPTER VII 

LIMITS AND UTS 129 

General considerations Limits In repetition manufacture 
Baaes for specifying limits Tolerance and allowance British 
Standard limits and Pits Mating and non-mating surfaces 
B E 8 A. standard tables Size multipliers and range factors 
Standard fits Specifying fits Workshop and Inspection 
gauges Newull limits Screw gauges and limits 

BIBLIOGRAPHY 148 

INDEX 151 




ILLUSTRAT 

Generator comparator . . . . .<> 
Taper or inclination expressed as a ratio of 

linear distances . .... .17 

Part of a circle divided into degrees . . 17 

Typical graduation of a 12-in. steel rule . . 32 
A 3-in. rule with scale graduated across the ends 34 
Steel tape mounted on spring-controlled drum. 

in metal case . . ... .38 

Illustrating method of reading a vernier . . 40 
Oaliper gauge with vernier reading to lOOths of 

an inch . . .... .41 

Oaliper gauge with' verniers reading to lOOOths 

of an inch, and SOths of a millimetre . . 42 
Oaliper gauge with vernier reading to lOOOths 

of an inch ....... 44 

Steel slide rule or gauge ..... 44 

Workshop combination end bar and accessories . 46 

Simple cahper gauges, without vernier . 47, 48 

Firm joint calipers ..... 49 

Spring calipers ...... 52 

Screw-adjusting outside and inside calipers . 63 

Combined dividers, inside and outside calipers . 54 
Reversible inside and outside calipers with screw 
adjustment ...... 54 

Hermaphrodite calipers . . . .55 

Keyway spring calipers ..... 56 

Screw pitch gauges . . . . .69 

Imperial standard wire gauges ... 62 

Feeler or thickness gauge ... .67 
Typical set of plain plug and ring gauges . . 69 



Vlil ILLUSTRATIONS 



29-33. Internal and external limit gauges . 70-72 

34 / 

Q e ' f Adjustable plain caliper gauges, high and low limit 73,74 

36. Wickman adjustable caliper gauge, with threaded 

anvils ....... 75 

37. Simple depth gauge for direct reading at end 

of eliding bar ...... 77 

38. Depth gauge with vernier reading to TtnrT in. 78 
30. Hole and step gauge ..... 80 

4=0. Small set of slip gauges . . . ... 81 

41-44. Applications of slip gauges and accessories 82,83 

4e 'P Micrometer cahper reading to unrnin.. . 86, 87 

47. Skeleton view of the mechanism of a micrometer 

caliper ....... 88 

48. Illustrating method of reading a " ten- 

thousandth " micrometer caliper . . 89 

49. Direct reading micrometer .... 91 

60. Micrometer cahper for measuring pistons . 94 

61. The Slocomb micrometer cahper ... 95 

62. Hub micrometer caliper .... 96 
58. Micrometer for sheet metal ... 97 

54. Micrometer depth gauge . . . .98 

55. Scribing micrometer for gear teeth, etc. . . 93 

56. Micrometer caliper head . . . .100 

67. Inside micrometer cahper set . . . .100 

68. ) Illustrating method of generating surface plates 
59 -i 103, 104 
60. Typical surface plates ..... 105 

ft i 1 

62 ; [ Scribing blocks ..... 108,109 

63. Steel try square . . . . . .110 

64.) 

Qg r Combination squares . . . . .112 

6 6-68 .Bevel protractors with and without verniers 1 1 3-1 1 6 

69. Illustrating method of reading an angular vernier 116 

70. Draughtsman's protractor . . . .116 

71. Dial test gauge ...... 1 



TABLES 




I. Decimal Equivalents of Fractions of an Inch 3 

II. Equivalents of Inches in Millimetres . . 5 

II. Equivalents of Millimetres in Inches . . 7 

[V. Tapers and Angles . . . . .19 

V. Minutes and Seconds as Decimals of a Degree 20 

\7I. Equivalents of Pounds in Kilograms . . 23 

II. Equivalents of Kilograms in Pounds . . 24 

II. Specific Gravities of Various Materials . 26 

X. Formulae for Surface Areas ... 28 

X. Formulae for the Volume of Solids . . 28 

1 . Shrinkage Allowances for Castings in Various 

Metals 35 

II. Imperial Standard Wire Gauge ... 64 

II. Birmingham (Stuhbs) Wire Gauge . . 65 

[V. American (Brown & Sharpe) Wire Gauge . 66 

IV. Birmingham Sheet Iron Gauge . . .66 

71. British Standard Limits for Unilateral, 

Bilateral, and Oversize Holes . .136 

II. British Standard limits for Standard Shafts 138 

II. Typical Examples of British Standard Fits 

of Standard Shafts . . . .141 

X. Values of Range Factor for Various Classes 

of Fits in Unilateral and Bilateral Holes. 144 

JX. Newall Allowances for Various Classes of 

Fits 147 



WORKSHOP 



LASURING 




CHAPTER I 

STANDARD UNITS OP MEASUREMENT 

Bar Measurements. 

a simplest form of measurement consists in 
ing some standard length as a unit, and ex- 
jsing the linear distance between two points 
:erms of this unit, its multiples or subdivisions. 
j linear units recognized in this country are the 
bish standard the yard, and the Continental 
idard the metre. 

Standard Yard. 

'he length of the standard yard is purely arbi- 
y, and is defined by Act of Parliament* as 

ows 

ae straight line or distances between the centres of the 
averse lines in the two gold plugs in the bronze bar deposited 
he office of the Exchequerf shall be the genuine standard 
L at 62 F., and if lost it shall be replaced by means of its 
es 

18 and 19 Viet , c 72, July 30th, 1855. 
In accordance with the Weights and Measures Act of 1878, 
British standards of measurement are now deposited at the 
idards Office of the Board of Trade ; copies of the standard 
1 are kept at the Houses of Parliament, the Mint, the Royal 
ety of London, the National Physical Laboratory and at the 
al Observatory, Greenwich 



2 WORKSHOP GAUGES 

The bronze bar in question is one inch square 
in cross section and thirty-eight inches long. A 
small gold stud is inserted at a distance of one inch 
from each end of the bar, and it is on the faces of 
these two studs that the transverse lines giving the 
standard unit of one yard are engraved. The 
standard is exact only when measurement is made 
at a temperature of 62 F., the distance between 
the lines being greater at higher (and less at lower) 
temperatures. 

Divisions of the Yard. 

The yard as a unit of measurement is obviously 
too long for the measurement of small work, and 
consequently it is divided into three equal parts, 
termed feet ; 'a foot is again subdivided into twelve 
equal parts termed inches. Where British units 
are employed, practically all workshop dimensions 
are expressed in terms of feet and inches. 

Fractions and Decimal Subdivision. 

Parts of an inch may be indicated either as 
fractions or as decimals. In the fractional system, 
the figure below the cross line, or at the right of 
the diagonal line, is termed the " denominator," 
and indicates the number of parts into which the 
inch has been divided ; while the figure above the 
cross line, or to the left of the diagonal line, is the 
" numerator," and indicates the number of these 
parts in the dimension to be expressed. Usually 
the binary system of fractions is employed, in which 
each subdivision is one-half the value of the preced- 
ing division, i.e. |, J, , ^, -fa, ^ ; this system has 



UNITS OF MEASUREMENT 3 

>ome the accepted method of subdivision of the 
h for the majority of work, though in some 
tances, e.g. in connection with gear wheel dimen- 
tis, odd fractions, such as -J , f , ^, are employed 
.h advantage. In very fine work, such as where 
Ler gauges are used (see p. 67), it is usual to 
jress measurements in thousandths of an inch. 
!n the decimal system of subdivision, the method 
building up a whole number in multiples of ten 
employed also in dealing with fractions less than 
ty. The first figure after the decimal point has 
unity value of one-tenth of one ; the second 
ire after the decimal point has a unity value of 
3-hundredth of one , the third, one-thousandth 
one ; the fourth one ten-thousandth of one ; 
I so forth. Each succeeding figure indicates a 
mber of divisions, each of which has one-tenth 
> unity value of the preceding division. Thus, 
416 inch signifies three inches plus one-tenth 
is four hundredths plus one-thousandth plus 



TABLE I 

Dm-m-M-AT. EQUIVALENTS OB 1 ITBAOTTONS OB 1 AN 



A 


03125 


1 


37600 


43 


71875 


x 


06250 


* 


40625 


f 


76000 


A 


09375 


A 


43750 


H 


78126 


1 


12500 





46876 


H 


81250 


A 


15626 


* 


60000 





84375 


A 


18750 


IX 


53125 


1 


87600 


& 


21875 


A 


66250 


M 


90626 


V 


25000 


W 


59375 


H 


93750 


13 


28125 


I 


62600 


H 


96875 


A 


31250 


w 


65625 


1 


1-00000 





34375 


H 


88750 







4 WORKSHOP GAUGES 

six ten-thousandths of an inch, i e. three complete 

one thousand four hundred and sixteen 

inches and -. : 

ten thousandths of an inch 

The decimal equivalents of various fractions of 
an inch are given in Table I. 

The Metre. 

The use of the metre* as a unit of length through- 
out Great Britain was legalized by Act of Parliament 
in 1907. Unlike the standard yard in its origin, 
the metre was intended to be a precise relation of 
the earth's dimensions, and it was stated to be 
one ten-millionth of the distance between the 
North Pole and the Equator, measured over the 
surface of the earth along the meridian passing 
through Paris. The original measurement of the 
arc of this meridian was carried out by Delambre 
and Mechain between Barcelona and Dunkirk, 
and the original standard metre was constructed 
by Borda. Actually, however, there were certain 
errors in the original calculation of the metre, and 
it is now defined as the distance between the two 
ends of the platinum rod originally constructed 
by Borda, the measurement being carried out at a 
temperature of Centigrade (32 Fahrenheit), f 

The relation between the metre and the yard is 

1 metre = 1-093633 yard = 39-37079 inches 
1 yard = 9143935 metre 

* The metre became the French standard unit of length in 
iccordance with the law of the French Republic in 1796. 

f Of the temperature of 62 F. at which the British standard 
rard is to be measured, and see pp. 1 and 2 In America several 
irms are standardising the metre at 68 F and 62 F , but in 
England the metre is legally standard at 00 



TTNTTS OF MEASUREMENT 



TABLE II 

JXJIVALENTS OB 1 INCHES AND FRACTIONS OB 1 AN INCH 



0* 


I" 


2* 


3* 


4' 


5* 


0794 
1-587 
2381 


25-399 
26-193 
26-987 
27-781 


50799 
51-593 
62-387 
53-180 


76-199 
76992 
77-786 
78 680 


101 59 
10239 
103 18 
103-97 


12690 
127-79 
128-58 
12937 


3 175 
3-969 
4762 
6656 


28-674 
29-368 
30-162 
30966 


53-974 
54-768 
56 561 
56355 


79374 
80-167 
80961 
81-756 


104-77 
10556 
10636 
107 15 


130 17 
13096 
131 76 
132-55 


6350 

7 144 
7937 
8731 


31-749 
32543 
33337 
34-131 


67 149 
57 943 
58736 
59 530 


82-549 
83-342 
84-136 
84930 


10794 
10874 
10953 
11032 


13334 
13414 
13493 
13572 


9525 
10319 
11 112 
11 906 


34924 
35718 
36612 
37 306 


60 324 
61 118 
61 911 
62705 


85-723 
86-517 
87-311 
88-105 


111 12 
111-91 
112-71 
113-60 


13662 
137-31 
138-11 
138-90 


12700 
13494 
14287 
16081 


38-099 
38-893 
39-687 
40-481 


63499 
64293 
65086 
65 880 


88-898 
89-692 
90-486 
91-280 


11429 
11509 
11588 
11667 


13969 
14049 
141-28 
14207 


16876 
16668 
17-462 
18-256 


41-274 
42068 
42862 
43-655 


66 674 
67468 
68261 
69055 


92-073 
92-867 
93-661 
94-455 


11747 
11826 
11906 
119 85 


14287 
14366 
144-46 
145-26 


19050 
19-843 
20-837 
21431 


44-449 
45243 
46037 
46830 


69 849 
70 642 
71 436 
72 230 


95248 
96042 
96836 
97 629 


12064 
12144 
122-23 
123-02 


14604 
146 84 
147 63 
14842 


22-226 
23-018 
23812 
24606 


47-624 
48418 
49-212 
60-005 


73 024 
73 817 
74611 
75405 


98423 
99217 
100011 
100 804 


123-82 
12461 
12541 
12620 


14922 
150-01 
150-81 
151 60 



WORKSHOP GAUGES 



TABLE II (continued) 
EQUIVALENTS OP INCHES AND FBAOTIONS OF AN INCH 

IN MHiUMHTBBlS 



6' 


7' 


8* 


9' 


10' 


11* 


Inches 


152-39 
153 19 
15398 
15477 


177-79 
178-69 
17938 
180-17 


203-19 
20399 
204-78 
20567 


22859 
22939 
23018 
23097 


253-99 
25478 
25558 
256-37 


279-39 
280-18 
28098 
281-77 




A 


16567 
166-36 
157-16 
167-95 


180-97 
181-76 
182-55 
18335 


206-37 
207-16 
207-96 
208-75 


231-77 
23256 
233-35 
234-16 


257 17 
257 96 
258-76 
259-55 


282-57 
28336 
284-15 
28495 


A 

T * 
A 


168-74 
159-54 
100-33 
161-12 


18414 
184-94 
185-73 
186-62 


209-54 
210-34 
211-13 
211-92 


23494 
235-73 
23653 
23732 


26034 
261-13 
261-93 
262-72 


28674 
28653 
28733 
28812 


A 
A 


161-92 
16271 
163-51 
164-30 


18732 
188-11 
18890 
18970 


212-72 
21351 
21430 
216-10 


238 12 
23891 
239-70 
240-50 


263-52 
26431 
265 10 
265-90 


288-92 
289-71 
29050 
29130 


3 


165-09 
165-89 
166-68 
16747 


19049 
191-29 
192-08 
19287 


215-89 
21669 
217-48 
21827 


241-29 
242-08 
242-88 
24367 


26669 
267-48 
268-28 
26907 


292-09 
292-88 
29368 
294-47 


4 
H 


16827 
169-06 
169-85 
17065 


193-67 
194-46 
196-25 
196-05 


219-07 
21986 
220-65 
22145 


244-47 
24526 
24605 
246-85 


269-87 
270-66 
27145 
27225 


295-27 
296-06 
296-86 
297-65 


I 

tf 
H 


171-44 
17224 
173-03 
17382 


196-84 
197-64 
198-43 
199-22 


22224 
223-04 
22383 
224-62 


247-64 
248-43 
24923 
260-02 


273-04 
27383 
27463 
27542 


29844 
29923 
300-03 
300-82 


t 


H 


17462 
176-41 
17620 
177-00 


200-02 
200-81 
201-60 
20240 


225-42 
22621 
227-00 
22780 


26082 
251-61 
262-40 
263-20 


27622 
277-01 
277 80 
27860 


30162 
302-41 
303-20 
304-00 


* 

if 



UNITS OF MEASUREMENT 



TABLE m 
EQUIVALENTS o? MTTJ.TMBTRBS m INCHHS 



Ins 


Mm. ' Ins. 


Mm. 


Ins 


Mm. 


Ins 


Mm. 


IDS. 


089 


51 


2008 


101 


8976 


161 


6946 


201 


7fllS 


079 


52 


2047 


102 


4-016 


152 


6984 


202 


7-968 


118 


68 


2-087 


103 


4055 


153 


6024 


208 


7-092 


167 


64 


2-126 


104 


4-006 


164 


6063 


204 


8082 


197 


55 


2165 


105 


4-134 


165 


6102 


205 


8071 


286 


56 


2205 


106 


4173 


166 


6142 


206 


8-110 


276 


67 


2244 


107 


4-213 


157 


6181 


207 


8-160 


315 


58 


2283 


108 


4-252 


158 


6-221 


208 


8-189 


854 


59 


2823 


109 


4291 


169 


6260 


209 


8-228 


894 


60 


2862 


110 


4-331 


160 


6209 


210 


8-268 


488 


61 


2402 


111 


4-870 


161 


6830 


211 


8-807 


472 


62 


2441 


112 


4409 


162 


6378 


212 


8347 


512 


63 


2480 


113 


4449 


168 


6417 


213 


8386 


551 


64 


2520 


114 


4488 


164 


6467 


214 


8426 


591 


65 


2669 


115 


4528 


166 


6496 


215 


8465 


680 


66 


2598 


116 


4567 


166 


6636 


216 


8-604 


669 


67 


2688 


117 


4606 


167 


6676 


217 


8543 


709 


68 


2677 


118 


4646 


168 


6614 


218 


8-683 


748 


69 


2717 


119 


4685 


169 


6-664 


210 


8622 


787 


70 


2766 


120 


4724 


170 


6-693 


220 


8661 


827 


71 


2705 


121 


4764 


171 


6732 


221 


8701 


866 


72 


2-835 


122 


4803 


172 


6772 


222 


8-740 


906 


73 


2874 


123 


4843 


178 


6811 


223 


8-780 


945 


74" 


2913 


124 


4882 


174 


6860 


224 


8-819 


984 


76 


2953 


125 


4021 


176 


6890 


225 


8868 


L-024 


76 


2-992 


126 


4961 


176 


6920 


226 


8-898 


L063 


77 


3-032 


127 


5000 


177 


6969 


227 


8-037 


L102 


78 


3071 


128 


5030 


178 


7008 


228 


8-076 


L142 


79 


3-110 


129 


5070 


179 


7047 


229 


9-016 


L181 


80 


3150 


130 


5118 


180 


7087 


230 


9066 


220 


81 


3-189 


131 


5-158 


181 


7126 


231 


9005 


260 


82 


3228 


132 


5107 


182 


7166 


232 


0184 


299 


83 


3-268 


133 


5236 


183 


7205 


233 


9-178 


330 


84 


3307 


134 


5276 


184 


7244 


234 


9-213 


878 


85 


3346 


136 


6315 


185 


7-284 


285 


9-262 


417 


86 


3386 


136 


5354 


186 


7323 


236 


9-201 


457 


87 


3426 


187 


5-304 


187 


7362 


287 


9-331 


496 


88 


8466 


188 


6433 


188 


7402 


288 


9-870 


535 


89 


3504 


139 


5472 


189 


7441 


239 


0410 


576 


00 


3643 


140 


5512 


100 


7480 


240 


0440 


614 


91 


8688 


141 


I 5551 


101 


7520 


241 


[ 9-488 


654 


02 


8622 


142 


6691 


102 


7659 


242 


0-528 


693 


03 


3661 


143 


5630 


103 


7508 


243 


0-667 


782 


04 


8701 


144 


5669 


104 


7638 


244 


0-606 


772 


06 


3740 


145 


5709 


106 


7677 


245 


0646 


811 


06 


3780 


146 


6748 


106 


7-717 


246 


0686 


860 


07 


3819 


147 ( 


1 5787 


107 


7756 


247 


0724 


890 


08 


3-858 


148 


6827 


108 


7-796 


248 


[0764 


929 


09 


8898 


149 


5-866 


109 


7885 


249 


0803 


969 


100 


8937 


150 


5-906 


200 


7874 


260 


0-843 



83) 



WORKSHOP GAUGES 



TABLE m (continued) 

OF UUJJHBXRBS is INCHES 



Mm. Ins. 


Mm. Ins 


Mm. Ins 


Mm InB. 


Mm. Ins. 


261 9 882 


301 11 860 


351 18 819 


401 16-788 


461 17-766 


252 9-921 


802 11 890 


852 18 868 


402 16-827 


462 17-795 


268 9 961 


308 11 929 


363 13-898 


403 16 866 


463 17 835 


264 10 000 


804 11 069 


354 13-987 


404 16 906 


454 17-874 


266 10 039 


306 12 008 


855 13 977 


405 16 945 


465 17 914 


266 10 079 


306 12 047 


856 14 016 


406 16 984 


466 17 953 


267 10-118 


807 12 087 


367 14 055 


407 16-024 


457 17 992 


268 10 16<3 


308 12 126 


358 14-095 


408 16-003 


458 18 032 


269 10-197 


309 12 166 


369 14 184 


409 16-103 


459 18 071 


260 10 286 


310 12 206 


360 14 173 


410 16-142 


460 18-110 


261 10 276 


311 12 244 


361 14 218 


411 16 181 


461 18 150 


262 10 316 


312 12 284 


362 14 262 


412 16 221 


462 18-189 


263 10-364 


318 12 323 


363 14 291 


418 16 260 


463 18-229 


264 10 894 


314 12-862 


364 14 831 


414 16 299 


464 18-268 


266 10 483 


316 12 402 


365 14 870 


416 16 339 


466 18-807 


266 10-473 


316 12 441 


366 14-410 


410 16 378 


406 18-847 


267 10 612 


817 12 480 


367 14 449 


417 16 417 


467 18-386 


268 10 661 


318 12 520 


868 14 488 


418 16 457 


468 18-425 


269 10 691 


319 12-669 


369 14 628 


419 16-496 


469 18-465 


270 10-630 


320 12-599 


870 14-567 


420 16 686 


470 18 604 


271 10 669 


321 12 638 


871 14 606 


421 16 576 


471 18 543 


272 10-709 


322 12 677 


372 14 646 


422 16 614 


472 18 583 


278 10-748 


328 12 717 


373 14-685 


423 16 654 


478 18 622 


274 10-787 


324 12-756 


374 14-726 


424 16 693 


474 18 662 


276 10 827 


325 12-795 


375 14 764 


425 16 732 


475 18 701 


276 10 866 


326 12-835 


376 14 803 


426 16 772 


476 18 740 


277 10-900 


827 12 874 


377 14-843 


427 16 811 


477 18 780 


278 10 946 


328 12-913 


378 14-882 


428 16 851 


478 18 819 


279 10-984 


329 12 963 


379 14 921 


429 16-890 


479 18 868 


280 11 024 


330 12 992 


380 14 961 


430 16 929 


480 18-898 


281 11-063 


381 13-032 


381 15 000 


431 16 969 


481 18-937 


282 11-102 


332 18 071 


382 16 040 


432 17 008 


482 18 977 


288 11-142 


333 13-110 


383 15 079 


433 17 047 


483 19 016 


284 11-181 


834 13-150 


384 16 118 


484 17 087 


484 19-055 


286 11 221 


336 13 189 


386 15 158 


485 17 126 


485 19 096 


286 11 260 


836 13-228 


386 16 197 


486 17-166 


486 19 134 


287 11-299 


S37 13-268 


887 15 236 


487 17-206 


487 19-178 


288 11-839 


338 13 807 


388 15-27(1 


438 17 244 


488 19 218 


289 11 378 


839 13 847 


389 15 815 


4-39 17 284 


489 19 262 


290 11-417 


340 13 886 


390 15 854 


440 17 828 


490 19*292 


291 11 467 


841 13 425 


391 15-894 


441 17-362 


491 19 881 


292 11-490 


342 13-465 


392 16 433 


422 17-402 


492 19 870 


298 11 636 


848 13 504 


893 15 473 


443 17-441 


498 19-410 


294 11 676 


844 13 548 


394 15 612 


444 17 480 


494 19-449 


296 11 614 


846 13-583 


896 16-551 


446 17 520 


496 19-488 


296 11 664 


346 13 622 


396 15 691 


446 17 569 


496 19-528 


297 11-693 


847 13 662 


397 15 630 


447 17 699 


497 19-567 


298 11-732 


848 13-701 


898 15-669 


448 17 688 


498 19-606 


299 11-772 


849 13 740 


899 15 709 


449 17 677 


499 19-646 


800 11 811 


850 13 780 


400 16 748 


450 17-717 


500 19-685 



UNITS OP MEASUREMENT 



TABLE HI (continued) 
EQUIVALENTS OF MILLIMETRBS m INCHES 



i Ins 


Mm. Ins. 


Mm T na 


Mm Ins. 


Mm. Ina. 


10726 


551 21 603 


601 23 662 


651 26 630 


701 27-600 


! 10 764 


552 21-782 


602 23 701 


662 26 670 


702 27-688 


I 10 803 


668 21 772 


60S 23 740 


653 26 700 


708 27 677 


19843 


564 21 811 


604 28 780 


654 25 748 


704 27 717 


10882 


656 21-861 


606 23-810 


655 26 788 


706 27-766 


10021 


556 21 800 


606 23 858 


656 25 827 


706 27-706 


10061 


567 21 020 


607 23 80S 


667 25-866 


707 27-886 


20000 


658 . 21 060 


608 23 037 


658 25-006 


708 27-874 


20040 


650 22 008 


600 23 077 


650 25 045 


"700 27 014 


20070 


560 22 047 


610 24 016 


660 25 084 


710 27 068 


20118 


561 22-087 


611 24 065 


661 26 024 


711 27-002 


20-158 


562 22 126 


612 24 006 


662 26 063 


712 28 082 


20107 


563 22 166 


613 24-134 


663 26 103 


713 28 071 


20286 


564 22 206 


614 24-173 


664 26 142 


714 28 110 


20276 


566 22 244 


615 24-213 


665 26-181 


716 28-150 


20-315 


566 22 284 


616 24 262 


666 26 221 


716 28-180 


20-855 


567 22 323 


617 24 202 


667 26 260 


717 28 220 


20304 


668 22-362 


618 24 331 


608 26 200 


718 28 268 


20433 


560 22-402 


610 24 370 


660 26 330 


710 28-807 


20473 


570 22 441 


620 24 410 


670 26 378 


720 28-347 


20-512 


571 22 481 


621 24-440 


671 26 418 


721 28-386 


20-551 


572 22 520 


622 24 488 


672 26 457 


722 28-425 


20-501 


573 22 660 


623 24 528 


673 26 406 


728 28-465 


20-630 


574 22 600 


624 24 567 


674 26 536 


724 28-504 


20-660 


676 22 638 


625 24 607 


676 26 575 


725 28-544 


20-700 


676 22 677 


626 24 646 


676 26 614 


726 28 583 


20-748 


577 22 717 


627 24 686 


677 26 654 


727 28 622 


20788 


678 22 756 


628 24 726 


678 26 603 


728 23-662 


20827 


670 22 706 


620 24 764 


670 26 783 


720 28-701 


20866 


680 22 836 


630 24 803 


680 26 772 


730 28-740 


20006 


581 22 874 


631 24 843 


681 26 811 


781 28-780 


20046 


582 22-014 


632 24-882 


682 26 851 


732 28 810 


20084 


683 22 063 


633 24 021 


683 26 800 


733 28 860 


21024 


684 22 002 


634 24 061 


684 26 020 


734 28 808 


21063 


686 23 032 


636 26-000 


685 26 060 


735 28-037 


21103 


686 23 071 


636 25 040 


686 27-008 


736 28 077 


21142 


687 23 110 


637 25 070 


687 27 047 


737 20 016 


21181 


688 23 150 


638 25 118 


688 27 087 


738 29-065 


21221 


580 23 l&O 


630 25 168 


680 27 126 


730 20 005 


21260 


500 23-220 


640 25 107 


600 27 166 


740 29-184 


21200 


501 23-268 


641 25-236 


601 27 205 


741 29 178 


21330 


502 23 307 


642 25 276 


602 27-244 


742 29-218 


21-378 


508 23*847 


648 25-815 


603 27-284 


748 29-262 


21-418 


504 23-386 


644 25-355 


604 27 323 


744 29 202 


21467 


605 23 426 


645 25-304 


605 27-862 


745 29-331 


21406 


606 28 464 


646 25 433 


606 27 402 


746 29 370 


21-586 


507 23-508 


647 25 473 


607 27-441 


747 29 410 


21676 


508 23-543 


648 25 612 


608 27-481 


748 29 440 


21-614 


600 28 582 


640 25 551 


600 27 520 


740 20-488 


21-664 


600 23 622 


650 25-601 


700 27 660 


760 29-628 

ni^m-~ - 





Z( LIBRARY. 



10 



WORKSHOP GAUGES 



TABLE III (continued) 
EQUIVALENTS OF MILLIMETRES ra INCHES 



Mm Ins. 


Mm. Ins 


Mm Ins 


Mm. Ins 


Mm. Ins 


751 20 56- 


801 31 536 


851 83 504 


901 35 478 


951 87-441 


752 29 60- 


802 31-575 


852 33 544 


902 36 512 


952 37 481 


753 29-646 


803 81 614 


863 33 5&3 


003 35-562 


958 37-520 


754 29 635 


804 31-654 


854 33 622 


904 35 601 


954 37 650 


755 29 725 


805 31 693 


856 83 662 


005 35 630 


955 37 500 


756 29 764 


806 31 733 


866 33 701 


006 36 670 


956 37 638 


757 29 803 


807 81-77L 


857 33 740 


007 35 700 


957 87 677 


758 29 843 


808 31-811 


858 33 780 


008 36 748 


958 87 717 


759 29 882 


809 31-851 


860 83 810 


009 35 788 


959 87 756 


760 29 922 


810 31-890 


860 33-850 


010 36 827 


960 37 706 


761 29 961 


811 31 920 


861 33-808 


Oil 35 866 


961 87-836 


762 30 000 


812 31 060 


862 38 937 


012 35 006 


962 37 874 


763 30-040 


813 32 008 


863 38 077 


013 35 045 


963 37 914 


764 30 070 


814 32 043 


864 34 010 


014 86 085 


964 37 953 


765 30 113 


815 32 087 


865 34 055 


015 30 024 


965 37 992 


766 30153 


816 32-120 


866 34 005 


016 36 063 


966 38-032 


767 30 197 


817 32 100 


867 34 134 


017 36 103 


967 38 071 


768 30 236 


818 32 205 


868 34 174 


018 36 142 


068 38 111 


769 30 276 


819 32 244 


860 34 218 


019 36-181 


969 88 150 


770 30 315 


820 32 284 


870 34 252 


020 36-221 


970 88 189 


771 30 355 


821 32 323 


871 34 202 


021 86 260 


971 38 229 


772 30 394 


822 32 362 


872 34 331 


022 36-300 


072 88 268 


773 30 433 


823 32-402 


873 84 370 


028 86 830 


078 88 307 


774 30 473 


824 32 441 


874 34 410 


024 36 878 


974 38 347 


775 30 512 


825 32 481 


875 34 449 


025 36 418 


976 38 886 


776 80-551 


826 32 620 


876 34-488 


026 36 467 


976 38 426 


777 30 591 


827 32 550 


877 34 528 


027 36 496 


977 88-466 


778 30 630 


828 32-590 


878 84 667 


028 36 530 


978 38 604 


779 30 670 


820 32-638 


870 34 607 


020 36-675 


979 38 544 


780 30 709 


830 32 677 


880 34646 


930 36 616 


980 38 583 


781 30-748 


831 32 717 


881 34 685 


081 86-654 


981 38-622 


782 30 7S8 
783 30827 
784 30-886 
785 30 906 
786 80 945 
787 30 985 
78S 31-024 
789 31-063 
790 81 103 


832 32-750 
833 82-796 
834 32835 
835 82 874 
836 32-914 
837 32 953 
838 32 992 
839 38032 
840 83-071 


882 34 725 
888 34-764 
884 34803 
886 84 848 
886 34882 
887 34-922 
888 34 961 
880 35000 
890 35 040 


032 86 603 
083 36 733 
084 36 772 
986 86 811 
036 86 861 
087 86 800 
038 36 020 
030 36 969 
040 37 008 


982 38 662 
983 38-701 
984 88 741 
985 38780 
986 38 810 
987 38-860 
988 38-808 
989 38-037 
990 38 977 


791 31-142 
792 81-181 
793 31-221 
794 31-260 
795 31-299 
796 31-339 
797 31 378 
798 31 418 
709 81 457 
800 31 496 


841 38 111 
842 83 150 
843 88 189 
844 33 229 
845 83-268 
846 33 807 
847 33 347 
848 33 886 
849 83425 
850 33 465 


891 35 079 
892 36 118 
893 35 158 
894 35 197 
895 35 237 
896 35 276 
897 35 316 
898 35 855 
890 35 304 
900 36 483 


941 37-048 
942 37 087 
943 87 126 
944 37-166 
946 37-206 
146 87-244 
147 87 284 
94? 37-323 
140 87 863 
60 87 402 


991 30-018 
092 89 056 
993 30-096 
094 80-184 
)96 39-174 
906 30-218 
007 80-252 
998 30 202 
099 30 831 
000 80-370 



UNITS OF MEASUREMENT 11 

ie metre is divided into 10 decimeters (a term 
3m used in measurement) ; the decimeter is 
led into 10 centimetres, and the centimetre 

10 millimetres. Measurements smaller than 
millimetre are referred to as fractions or decimals 

millimetre. 

mversions of British into Continental measure- 
ts, inches to millimetres and vice versa, are 
a in Tables II and III. 

jurement by Comparison. 

ie fundamental principle of all linear measure- 
fc consists in comparing, either directly or 
ectly, the distance between two or more points 
>ne object with the distance between two or 
5 points on some other object. Measurement, 
;B general sense, does not necessarily involve 
use of numerical values or of graduated scales 
mon examples of measurement by direct 
panson are seen when two pieces similar in 
Dr shape are placed together or are superimposed 
one on the other for checking purposes, or 
i a piece of cylindrical form or circular section 
sted in the hole of another piece into which it 
tended to fit. Limit gauges (see p. 72) provide 
ler examples of direct comparison of dimensions 
are largely used in modern workshop practice, 
imiliar examples of indirect comparison are 
when a pair of calipers (see p. 46) is first 
sted to fit over one piece of work or over a 
3rn, and is then tried over another piece in 
ess of manufacture ; when an adjustable depth 



12 WORKSHOP GAUGES 

gauge (see p. 77), is first set to the length of a plug 
and is then tested in the hole into which the plug 
is to fit ; and when a template which has been 
made as a pattern is superimposed on the piece in 
process of manufacture as a check either on the 
work in progress or on the final completion of the 
work. In all methods of checking such as the above, 
measurement is made entirely by comparison and 
numerical values are not necessarily brought into 
use. 

Generation of Length Standards by Comparison. 

The importance of possessing accurate standards 
of length will be evident from what has already 
been said, and will be increasingly apparent from 
the later pages of this book. Without such 
standards, quantitative measurements would be 
an impossibility 

Subdivisions of standard lengths may be made 
by aid of a suitably calibrated measuring machine 
but, for the highest precision, it is best to adopt 
the system of " direct generation," which it is pro- 
posed to describe briefly, because it affords an 
excellent example of measurement by comparison, 
and a striking justification for Whitworth's predic- 
tion, made more than seventy years ago, that 
further advances in fine measuring depended 
principally upon truly flat surfaces. 

The practicability of " generation of size " to a 
degree of accuracy suitable for the purpose con- 
sidered depends upon making a new type of stand- 
ard bar with the ends truly flat, parallel, and square 



UNITS OF MEASUBEMENTS 13 

i the axis to an order of accuracy approaching 
-millionth of an inch. Surfaces of the requisite 
ree of flatness are prepared by lapping on a 
5 lapping plate (pp. 79, 102; see also Patent No. 
149-1922), and the necessary high-precision 
iparative measurements are made by means of 
generator comparator." 

he general appearance of the generator compara- 
in use is shown by J?ig. 1. A massive casting 
ies a levelling base on which there is a platen 
ible of being rotated so as to interchange two 
3 with regard to the contact balls of a high- 
jision level. The machine is entirely self- 
brating and self-adjusting without reference to 

exterior or previous calibration ; also, it is a 
ust piece of apparatus which can be used by 
average mechanic without special skill or pre- 
is experience. By means of the cross slides 
ve the level the whole of the upper surfaces of 

gauges resting upon the rotating platen can be 
Lored. 

parent bar is derived from the Legal Standard 
d and this can then be subdivided as required by 
process of direct generation. The actual manu- 
ure of a full set of subdivisions! standards 
iirally occupies a considerable length of time 

the principle employed is very simple and may 
compared with that used in the generation of 
ace plates (p. 102). The end bars or gauges 
ig compared are placed side by side in a vertical 
ttion on the rotating platen, and their relative 
;hts are compared directly by means of the 




Fitter Gauge <C Precinon Tool Co , Ltd 
FIG 1 GENERATOR COMPARATOR 

Simultaneous comparison of two 6 In. bars against a 12-m bar 



mnrs OP MEASUREMENT 15 

ion spirit level which spans aoross the ends of 
ITS. A little consideration will show that if any 
>very two of three bars are together exactly 

to a 12-inch bar then each of the shorter 
nust be exactly 6 in. long. By working to a 
be programme of manufacture, the shorter 
' generated " from a longer one can be made 
ianeously and progressively to approach the 
subdivision required, and the principle thus 
r outlined can be applied to the generation of 
iver subdivisions may be desired.* 

interesting point of great practical import- 
is that all bars so made from the same 
jnt " standard, using the " generator com- 
Dr," will be true to size at the temperature 
lioh the parent bar is correct, although the 
L manufacture is carried out at ordinary work- 
temperature This assumes, of course, that 
ITS are all of the same material. 
> two bosses or parts of larger diameter visible 
;h of the gauge bars in Fig 1 are called " nodal 
." Theij function is to support the bar at 
points that the ends of the bar remain truly 
el, whether the supporting surface be flat or 
horizontal or inclined. These bands arc 
d, symmetrically with regard to the centre 
3 bar, at calculated positions which enable 
to fulfil their intended purpose. 

,p a detailed explanation of the procedure adopted in 
atmg " a full series of standards, the reader may be re- 
fco a brochure entitled Accuracy vn Industry, issued by 
ter Gauge and Precision Tool Co , Ltd , Woolwich, 8. E.I 8, 
ing the processes invented at the National Physical 
tory by J. E Sears and A J C Brookes 



16 WORKSHOP GAUGES 

The large measuring area on bars of this type 
(viz. that corresponding to -in diameter) con- 
duces to accuracy and prolongs the service life of 
the bars, whilst extending their applicability to 
workshop use, especially in combination with 
standard block and slip gauges (p. 79). 

Eleven standard reference bars, of the following 
sizes in inches : 36, 30, 24, 18, 12, 6, 5, 4, 3, 2, and 
1, can be used singly, or in " wrung together " com- 
binations of two bars, to give all sizes from 1 to 
42 inches, advancing by single inches. If used in 
conjunction with a set of 36 slip gauges these bars 
provide over 400,000 sizes advancing by single 
ten-thousandths of an inch I 

It is claimed that the Fitter standard reference 
bars represent the world's highest accuracy in 
length measure up to 36 inches and, where necessary, 
they are guaranteed true to length within one part 
in a million in terms of the Imperial Standard 
Yard. 

The uses of measuring bars and slip gauges for 
various workshop purposes are described later. 

Angular Measurement. 

Angular measurement provides a means of 
expressing numerically the inclination to one 
another of any two lines or planes. The dimensions 
of an angle can be determined from the magnitude 
of two linear distances at right angles to one another, 
and this method is frequently used in stating the 
dimensions of an inclination or of a taper, e.g. 



-lyard- 



4k 



FIG. 2 TAPER OB iNoxnrATiON EXPRESSED AS A 
RATIO OP LINEAR DISTANCES. 

The Inclination of the line AB with regard to AC, or the taper 

of the shaded key, Is 1 In 20 
(Note. The line SO la at right angles to OA The length AB Is 

v/(20 + 1) = 20-025 approximately). 

The total taper of the two lines AB, At, Is 2 In 20 or 1 In 10. 
le Inclination of DE with regard to DF Is 1 hi. In 1 yd (or 1 In 3fl) 




f 



3. PABT OF A Cmoi,B DIVTDBD INTO DEGREES. 



17 



18 WORKSHOP GAUGES 

1 in 20, or 1 inch in 1 yard (see Fig. 2). It is, how- 
ever, more general, to express the angle between 
any two lines in terms of degrees or decimals of a 



In angular measurement by degrees the complete 
circle is divided into 360 equal parts, termed degrees 
(see Fig. 3). Two lines drawn from the centre of 
the circle to any two adjacent divisions are inclined 
to one another at one degree: 90 degrees, or the 
fourth part of one complete rotation of a line about 
a point is termed a " right angle." 

Each degree is divided into sixty minutes, and 
a minute is divided into sixty seconds. The estab- 
lished symbols indicating degrees, minutes, and 
seconds are respectively , ', " ; thus, 46 32' 45*. 

The division of a degree into minutes and seconds 
is used where great accuracy is required, but in 
ordinary workshop practice, it is generally more 
convenient to express an angular measurement of 
less than a degree as either a fraction or a decimal 
of a degree. Equal accuracy of expression is 
possible by this means for example 46-54583 is 
exactly the same angle as 46 32' 45" but the latter 
is the more convenient form, where this degree of 
precision is required. 

Table IV shows angular and other equivalents 
of various tapers, and Table V, giving the decimal 
equivalents of the minutes and seconds of an angle, 
will be found useful. 

Units of Mass. 

Determination of the weight of a finished part 



UNITS OP MEASUREMENT 



19 



TABLE IV 
TAPERS AND ANGLES 



er 
'oot 


Complete^ 
Angle 
Included 


Angle with 
Centre Line 


Taper 
Per Inch 


Taper 
Per Inch 
from. 
Centre 
Line 


Deg. 


Min 


Deg. 


Mm. 







36 





18 


010416 


005203 







54 





27 


015625 


007812 




1 


12 





36 


020833 


010416 




1 


30 





45 


026042 


013021 




1 


47 





53 


031250 


015625 




2 


05 


1 


02 


036458 


018229 




2 


23 


1 


11 


041667 


020833 




2 


42 


1 


21 


046875 


023438 




3 


00 


1 


30 


052084 


026042 




3 


18 


1 


39 


057292 


028646 




3 


25 


1 


47 


062500 


031250 




3 


52 


1 


56 


087708 


033854 




4 


12 


2 


06 


072917 


036456 




4 


28 


2 


14 


078126 


039063 




4 


45 


2 


23 


083330 


041867 




6 


58 


2 


59 


104666 


052084 




7 


08 


3 


34 


125000 


062500 




8 


20 


4 


10 


146833 


072917 




9 


32 


4 


46 


166666 


083332 




11 


54 


5 


57 


208333 


104166 




14 


16 


7 


08 


260000 


125000 




16 


36 


8 


18 


291666 


145833 




18 


54 


9 


27 


333333 


166666 




21 


14 


10 


37 


375000 


187500 . 




23 


32 


11 


46 


416666 


208333 




28 


06 


14 


03 


500000 


260000 




20 



WORKSHOP GAUGES 



TABLE V 

MINUTES AND SECONDS OF ABO EXPRESSED AS DECIMALS 
OF A ~ 



MIN 


0' 


10' 


20* 


30* 


40* 


50* 








00278 


00556 


00833 


01111 


01389 


1 


01667 


01944 


02222 


025 


02778 


03055 


2 


03333 


03611 


03888 


04166 


04444 


04722 


3 


05 


05278 


05555 


05833 


06111 


06388 


4 


06666 


06944 


07222 


075 


07777 


08055 


5 


08333 


08611 


08888 


09166 


09444 


09722 


6 


1 


1028 


1055 


1083 


1111 


1139 


7 


1167 


1194 


1222 


125 


1278 


1306 


8 


1333 


1361 


1388 


1417 


1444 


1472 


9 


15 


1528 


1556 


1583 


1611 


1639 


10 


1667 


1694 


1722 


175 


1778 


1805 


11 


1833 


1861 


1889 


1917 


1944 


1972 


12 


2 


2028 


2056 


2083 


2111 


2139 


13 


2167 


2194 


2222 


226 


2278 


2306 


14 


2333 


2361 


2389 


2417 


2444 


2472 


15 


26 


2527 


2555 


2583 


2611 


2639 


16 


2667 


2694 


2722 


275 


2778 


2806 


17 


2833 


2861 


2889 


2917 


2944 


2972 


18 


3 


3028 


3056 


3083 


3111 


3139 


19 


3167 


3194 


3222 


325 


3278 


3306 


20 


3333 


3361 


3389 


3417 


3444 


3472 


21 


35 


3527 


3555 


3583 


3611 


3639 


22 


3667 


3694 


3822 


376 


3778 


3806 


23 


3833 


3861 


3889 


3917 


3944 


3972 


24 


4 


4028 


4056 


4083 


4111 


4139 


25 


-4167 


4194 


4222 


425 


4278 


4306 


26 


4333 


4361 


4389 


4417 


4444 


4472 


27 


45 


4527 


4555 


4583 


4611 


4639 


28 


4667 


4694 


4822 


475 


4778 


4806 


29 


4833 


4861 


4889 


4917 


4944 


4972 



UlSriTS OF MBASUBEMENT 



21 



TABLE V (oontinued) 



0' 


10* 


20* 


80* 


40* 


60* 


5 


5028 


5056 


5083 


5111 


5139 


5167 


5194 


6222 


525 


5278 


5306 


5333 


5361 


5389 


5417 


5444 


5472 


56 


5527 


5555 


5583 


5611 


5639 


5667 


5694 


5822 


575 


5778 


5806 


5833 


5861 


5889 


5917 


5044 


5972 


6 


6028 


6056 


6083 


6111 


6139 


6167 


6194 


6222 


625 


6278 


6306 


6333 


6361 


6389 


6417 


6444 


6472 


65 


6627 


6565 


6583 


6611 


6639 


6667 


6694 


6822 


675 


6778 


6806 


6833 


6861 


6889 


6917 


6944 


6972 


7 


7028 


7066 


7083 


7111 


7139 


7167 


7194 


7222 


725 


7278 


7306 


7333 


7361 


7389 


7417 


7444 


7472 


75 


7527 


7655 


7583 


7611 


7639 


7667 


7694 


7822 


776 


7778 


7806 


7833 


7861 


7889 


7917 


7944 


7972 


8 


8028 


8056 


8083 


8111 


8139 


8167 


8194 


8222 


825 


8278 


8306 


8333 


8361 


8389 


8417 


8444 


8472 


85 


8527 


8555 


8583 


8611 


8639 


8667 


8694 


8822 


876 


8778 


8806 


8833 


8861 


8889 


8917 


8044 


8972 


9 


9028 


9056 


9083 


9111 


9139 


9167 


9104 


9222 


925 


9278 


9306 


9333 


9361 


9389 


9417 


9444 


9472 


95 


9527 


9555 


9583 


9611 


9639 


9667 


9694 


9822 


976 


9778 


9806 


9833 


9861 


9889 


9917 


9944 


9972 



22 WORKSHOP GAUGES 

or piece of work is sometimes of considerable import- 
ance, e g. in flywheel calculations and in connection 
with governor control. It is necessary, therefore, 
to refer briefly to the methods of calculating the 
mass or weight of material. 

The standard units of mass throughout Great 
Britain are the pound avoirdupois and the kilogram ; 
m workshop practice the pound avoirdupois is 
used almost exclusively in this country. As in the 
case of the standard yard the weight of the standard 
pound is purely arbitrary, and is the mass of a 
piece of platinum preserved at the Standards Office 
of the Board of Trade. 

The kilogram was intended to be a precise relation 
of an accessible commodity and was originally 
constructed by Borda to represent exactly the mass 
of a cubic decimetre of water at 4 Centigrade (the 
temperature at which water attains its maximum 
density). As in the case of the original measure 
of the metre, it is now known that Borda's measure- 
ment was not exact, and the kilogram is now 
defined as the mass of a piece of platinum 
preserved in Paris and termed the " kilogram des 
Archives." 

A pound avoirdupois is equal to 0-45359265 
kilogram, and a kilogram is equal to 2' 20462 125 
pounds. 

Values of British pounds in kilograms, and of 
kilograms in British pounds, are given in Tables 
VI and VII. 

If the mass of any volume of a given substance 
be determined, and the mass of the same volume 



UNITS OF MEASUREMENT 



23 



TABLE VI 
EQUIVALENTS or POUNDS IN KILOGRAMS 



Kilos 


Lbs Kilos. 


Lbs. Kilos 


Lbs. Kilos. 


45359 
90718 
1-36078 
1-81437 
2-26796 


26 11-79342 
27 12-24701 
28 12-70060 
29 13-15420 
30 13-60779 


61 23 13324 
52 23-58683 
53 2404043 
54 24-49402 
56 24-94761 


76 34-47307 
77 34-92668 
78 3538026 
79 36-83384 
80 36-28744 


2-72166 
3 17615 
3 62874 
4 08233 
4 63593 


31 1406138 
32 1461497 
33 1496857 
34 1542216 
35 1587575 


66 26-40121 
67 25-85480 
58 2630839 
69 2676199 
60 27-21558 


81 36-74103 
82 37 19462 
83 37 64822 
84 38-10181 
86 38-56540 


4 98952 
544311 
5 89671 
6-35030 
6-80389 


36 1632934 
37 1678294 
38 17-23663 
39 17 69012 
40 18 14372 


61 27-66917 
62 28 12276 
63 28-67636 
64 29-02995 
65 2948354 


86 3900900 
87 3946260 
88 3991618 
89 40-36977 
90 40-82337 


7-25749 
7-71108 
8 16467 
8 61826 
9 07186 


41 18-59731 
42 1906090 
43 19 50459 
44 19 95810 
45 2041168 


66 29-93714 
67 3039073 
68 3084432 
69 31 29791 
70 31 75151 


91 41-27696 
92 41-73065 
93 42 18415 
94 42 63774 
95 43-09133 


9 52545 
9 97904 
0-43263 
3-88623 
1-33982 


46 20 86627 
47 21-31887 
48 21-77246 
49 22-22605 
50 22-87965 


71 32-20510 
72 32-65870 
73 33-11229 
74 3356588 
76 3401947 


96 43-54493 
97 43 99852 
98 44-46211 
99 4490570 
100 46-35930 



5383) 



WORKSHOP GAUGES 



TABLE VII 
EQUIVALENTS or KILOGRAMS IN POUNDS 



Kiloa. Lba. 


Kilos Lba. 


Kilos. Lbs. 


Kilos Lbs. 


1 2-205 


26 57 320 


51 112-435 


76 167 560 


2 4409 


27 69 524 


52 114 639 


77 169 754 


3 6014 


28 61-729 


53 116 844 


78 171 959 


4 8-818 


29 63 933 


54 119 048 


79 174 163 


5 11-023 


30 66 138 


65 121-253 


80 176 369 


6 13 228 


31 68 343 


56 123 458 


81 178 573 


7 15 432 


32 70 547 


57 125-662 


82 180 777 


8 17 637 


33 72 762 


58 127 867 


83 182 982 


9 10 842 


34 74 956 


59 130-071 


84 185 186 


10 22 046 


35 77 161 


60 132 277 


85 187 391 


11 24251 


36 79-366 


61 134 481 


86 189 596 


12 26 455 


37 81 570 


62 136-685 


87 191 800 


13 28 660 


38 83 775 


63 138-890 


88 194 005 


14 30 864 


39 85-979 


64 141 094 


89 196-209 


15 33 069 


40 88-184 


65 143 299 


90 198416 


16 35 274 


41 90-389 


66 146-604 


91 200 619 


17 37-478 


42 92 593 


67 147-708 


92 202 823 


18 39-683 


43 94 798 


68 149 913 


93 206 028 


19 41 887 


44 97-002 


69 152 117 


94 207 232 


20 44 092 


45 99 207 


70 154-323 


96 209 437 


21 46 297 


46 101-412 


71 C 156527 


96 211 642 


22 48 501 


47 103 616 


72 158 731 


97 213 846 


23 60 706 
24 52 910 


48 105 821 
49 108 025 


73 160 936 
74 163-140 


98 216 051 
99 218 265 


25 55 115 


50 110-231 


75 166 345 


00 220 462 



UNITS OF MEASUREMENT 25 

Eiter, the first divided by the second gives the 
icific gravity " of the substance, or 

Mass of any volume of substance 



peoifio gravity 



Mass of equal volume of water 
Weight of any volume of substance 



Weight of equal volume of water 

iter has been adopted as a standard unit of 
since it is readily obtainable in a pure state, 
mogeneous, and has an invariable density at 
en temperature. 

e specific gravities of some of the more common 
ances met with in engineering are shown in 

>vin. 

lation of Weights. 

3 weight of 1 cu. ft. of water is, approximately, 
bs , so that, knowing the specific gravity of a 
*ial, we can calculate the weight of any piece 
therefrom, by aid of the formula 

bin Ibs = Volume, in cu ft x Specific gravity x 62-3 
= Volume, in cub ins X Specific gravity x 00361 

most practical purposes, it is more convenient 
rk with the " density " of the material which 
nod as the mass of unit volume of the material 
s of density in Ibs. per cu. in., and in Ibs. per 
. are also given in Table VIII, and the weight 
7 piece may be calculated from 

i m Ibs. = Volume, in cu ft. x Density, in Ibs. per cu. ft. 
= Volume, m cu ins. x Density, in Ibs per cu. in. 



26 



WOEKSHOP GAUGES 



TABLE 

SPECIFIC GBAVITEES AND DENSITIES or 1 COMMON SUBSTANCES 
( Approximate) 



Material 


Specific 
Gravity 


Density 


Lba. per cu. in. 


Lbs. per cu. ft. 


Water (fresh) 


1-0 


0-036 


623 


Oil light 


0-7-0-8 


025-0-029 


44-60 


heavy 


0-88-0 98 


0-032-0-035 


55-60 


Wood soft 


48-0-88 


0-0170-032 


30-65 


hard 


0-66-1-3 


0-02-0-048 


35-82 


Brickwork 


1-6-2 1 


058-0-075 


100-130 


Concrete 


2-2 


0-081 


140 


Aluminium and 








its alloys 


2-5-30 


009-011 


155-185 


Iron and steel 


7-2-7-9 


26-0-28 


450-490 


Copper, brass and 








bronze 


8-0-88 


29-0-32 


500-550 


Lead 


114 


0-41 


710 


Mercury 


13-6 


049 


850 



CHAPTER II 

SIMPLE MEASUREMENT 

)RE describing in detail the various instruments 
for measurement and gauging in ordinary 
shop practice, a brief statement of the method 
ilculating the results of some of the simpler 
3 of such measurement may be given, 
termination of a linear extent on a plane 
ce in terms of a standard unit is a direct 
jss: that is, the reading of the scale or the 
ace apart of the points of the calipers or other 
iment used gives the desired answer without 
calculation being necessary, 
sasurement of superficial area or of volumetric 
jity, however, involves the taking of at least 
limensions, and the area or the volume is some 
ict of these dimensions. 

it of Surface. 

e superficial area of certain geometrical figures 
tamed by simple calculation, and a few typical 
of such figures are given in Table IX. The 
r TT (= ratio of the circumference to the 
eter of a circle) = 3-1416 = 22/7 approximately. 

oremeut of Volumetric Capacity. 

me typical cases of geometrical figures are 
L in Table X, the factor TT being, as before, 
6 or 22/7 approx. 

27 



28 



WORKSHOP GAUGES 



TABLE IX 
FORMULAE FOR SURFACE AHE\S 



Figure 


Data 


Surface 


Square 


a = length of side 


a" 


Rectangle 


a and 6 = length of two 






adjacent sides 


ab 


Parallelogram 


a = height 






b = base 


ab 


Triangle 


a = height 






b = base 


{ab 


Circle 


T = radius 


m* 




d = diameter 


TcdV4 (= 7864<P) 


Sphere 


T = radius 


471^ (= 125607*) 


Cylinder 


r = radius 
A = height 


Curved surface = Zjwh 
Total, including ends 
= Z-nr(r+ A) 


Cone 


r = radius of base 


Curved surface (1 e 




A ~ height 


surface excluding 




/ = length of side (ape\ 


base) = itrl 




to Lose) = \/r* + IP 





TABLE X 
FORMULAE FOB. THE VOLUME OF So -IDS 



Figure 


Data 


V oluine 


Cube 


a = length of side 


a 1 


Rectangular parallel- 






sided body 


a, b, c = lengths of three 






adjacent edges 


ale 


Sphere 


r radius 


ITO* 




d = diameter 


<J 5236d" 


Cylinder or Prism 


r = radius of hose 






A = height 


aA or 7tr a A 




a = area of hose 




Cone 


a => area of basn 






r = radius of baso 






A = IvlRht 


JflA or 1 -m*h 



Parallax. 

In simple measurement it is of the first importance 
that instruments suitable in every way be used for 
the precise measurement involved. As an example 
of this, the measurement of the diameter of a sphere 
may be instanced ; in this case the edges or points 
of the measuring appliance must be brought into 



SIMPLE MEASUREMENT 29 

ite contact -with the dimensions to be measured, 
this is not effected, an appreciable error due 
parallax " may occur. Parallax may be 
d as the apparent change of position of an 
. relatively to other objects when the aspect 
en from a different point or points. Errors 
3 parallax have to be guarded against in all 
of simple measurement, and also in the use 
bruments for such purposes as land surveying, 
Lomical observations and the like. In the 
)f the measurement of the precise diameter 
phere, the dimension cannot be even approxi- 
y measured, without possibilities of grave 
by placing a rule over the object and attempt- 
gauge the dimension by the eye. Some such 
ment as a pair of calipers or similar instrument 
intial in obtaining a measurement of this kind. 
all cases where accurate observation is neces- 
the eye with which the measurement is to be 
must be perpendicularly in front of the point 
Dbserved. In order to ensure perfect definition 
.her eye of the observer should be closed. In 
a simple scale, the eye should first be placed 
ly vertical to the scale at the point where the 
bservation is to be made. The rule must then 
Ljusted so that its end, or, alternatively, a 
je graduation on the rule, is exactly comcident 
the first point at which the observation is 
made. Great care must then be taken to 
3 that the rule is not moved in relation to the 
i being measured until the completion of the 
i observation. The eye must then 




30 WORKSHOP GAUGES 

perpendicularly in front of the second point to be 
observed, and the calibration mark on the scale 
which coincides with this second point on the part 
to be measured must then be read off. When the 
zero calibration on the scale has been set to the first 
point to be observed, the reading on the scale of the 
second point observed is, of course, the linear 
dimension required , where some other calibration 
mark has been taken for the first point observed, the 
required measurement is the reading at the second 
point observed less the reading at the first point of 
observation. 

Linear Dimensions. 

The instruments in general use in engineering 
workshops for the determination of linear dimensions 
are rules, calipers of various sorts, micrometers, 
height gauges, depth gauges, thickness gauges, 
rod gauges, and caliper or map gauges. Of these 
the simple rule is of the greatest general service 

The Rule. 

All rules as used in engineering workshops consist 
of flat straight stnps of steel or other suitable 
material engraved on one or more edges with gradua- 
tion marks which represent definite and stated 
proportions of the standard units of linear measure- 
ment. Rules are now available in a considerable 
variety of material, shape and graduation, and 
there is no difficulty in obtaining a rule to meet 
any possible requirement of work and to suit any 
conceivable individu.il taste. Rules for use by 



SIMPLE MEASUREMENT 31 

aanics are almost invariably made of steel ; 
enters' and pattern makers' rules aro usually 
ard wood, e.g. box-wood ; and tho scales or 
i in use by draftsmen are usually of wood, ivory, 
>, celluloid or cardboard. 

rulo is generally rectangular in croas section, 
alternatively, has one or both edges bevelled 

For special purposes, rules having triangular, 
re, or elliptical cross section are sometimes 
Loyed. The width of rules may be anything 

J- in. to 2 in., the thickness from -^th to J in. 
the length from 1 in. up to 6 ft. or more : rules 
:> 12 in. in length are usually made in one piece, 
eas rules longer than this are generally made 
hinged sections, so that they can be folded up 
eniently when not in use 

nation of Rules. 

ie graduation of rules is carried out in a groat 
ifcy of ways. In some cases, scales aro engraved 
oth sides of the rule and along both edges, so 
four different scales are provided on the same 
; in other cases, one side of the rule only is 
ived, sometimes one scale being provided and 
itimes different scales being engraved along 
of the two edges. 

ith the British standard system of measurement 
are generally divided using the binary system 
actions, and in some cases the decimal system 
ed. Rules having combinations of these two 
ms of division are frequently employed. With 
Continental system of measurement, rules arc 



32 



generally divided into 
and half millimetres. It 



I 

=1 ^ r-"l fpq^ oo g 




millimetres, 
usually the practice 
to engrave the finer divisions 
along a portion only of the 
scale, a rule divided in this 
Wa -y being generally easier to 
read correctly than where the 
line divisions are engraved 
along the -whole length of the 
scale. A typical example of 
| a twelve-inch rule of this type 
is shown in Fig. 4 in this 
case, one edge of the rule is 
divided into centimetres and 
millimetres throughout, the 
first 6 centimetres being di- 
vided into half millimetres ; 
the second edge is divided 
into inches and sixteenths 
throughout, the first 3 inches 
are divided into 32nds, and 
half the fourth mch is divided 
into 64ths. 

By taking the completed 
inches in a dimension on the 
open portion of a scale and 
the fractional part of the 
dimension on the finely 
divided portion, any dimen- 
sion within the capacity of the scale can be 
readily determined. Where the required dimen- 
sion does not exactly coincide -with a graduation 



SIMPLE MEASUREMENT 33 

i the scale, the correct position that it 
ccupy on the scale between two adjacent 
! can be estimated, with a little practice, 

degree of accuracy 

imon method of calibrating a rule carrying 
erent scales on the two sides and along the 
;es is to divide the first scale into eighths, 
second into eighths and sixteenths, with the 
1 last inches divided into sixteenths and 
icondths respectively ; the third scale into 
und twentieths, with the first and last inches 
Jhs and hundredths ; and the fourth scale 
)lfths and twenty-fourths. On many rules 

scale is provided, arranged down the centre 
ale (i.e. between two of the scales), or else 
he place of one of the inch scales along one 

in Fig. 4) 

tting Rules. 

[nations of the binary fractional system 
he decimal system are frequently used. A 
HI employed on gear-cutting work has four 
'aduated as follows 

. lOths, 20ths, 60tha and lOOths 

. 12ths, 24the and 48the 
. 16ths, 32nds and 64ths 
14ths and 28ths 

)ecial purposes some rules carry an additional 
scales graduated across one or both ends, 
i rule of this type is illustrated in Fig. 5, 
38 shown being inches and eighths along one 
id inches, eighths and sixteenths along the 
edge ; the scales engraved along the two 



n-1 WORKSHOP GAUGES 

edges of the rule show thirty-seconds of an inch 3 
the graduation being carried out from the bottom 
edge only of the scale and extending to a total oi 
14 '32nds of an inch across each end of the scale. 

Metric Rules. 

Steel rules for workshop use are generally procur- 
able in all lengths, ranging from five centimetres 
up to a metre. They usually carry two scales only, 
and are graduated into millimetres along one edge, 
and into millimetres and half millimetres along the 




L S Starrett Co , Ltd 

FIG. 5 A 3-nsr BTJLE WITH SCAIJIS GBADUATED 
ACROSS THE ENDS 

second edge Scales are sometimes engraved along 
one or both ends. 

Metric and British Standard Rules. 

In certain classes of work it is sometimes a great 
convenience to be able to read direct at will in either 
British or Continental standard measurement, and, 
for this purpose, special rules with metric and British 
standard scales are available. The graduation 
is generaUy in millimetres and half millimetres 
along one edge, and in inches, sixteenths and thirty- 
seconds along the other edge. Rules of this type 
are generally obtainable in lengths of from 5 centi- 
metres (1-9685 inches) up to a metre (39-37 inches). 



SIMPLE MEASUREMENT 



35 



nkage or Contraction Rules. 

or all ordinary measurement one or other of 
numerous patterns of standard rules is used, 
attern maker, however, when making a pattern 
i which a casting is to be produced, uses a 
ial rule in which the true distances apart of the 
luations are greater than those represented on 
scale, since allowance has to be made for the 
ikage of the casting after the metal has been 
*ed into the mould made in the sand. The 
perature of the molten metal is, of course, very 
, and as the casting cools it shrinks, and the 
ern used must, therefore, be slightly larger than 
finished casting is required to be. The amount 
irinkage varies with the material being cast, and, 
)me cases, with the nature of the casting.* 
ae usual allowances made with various materials 
>ach foot in length are as follows 

TABLE XI 

<TKAGB ALLOWANCES IOB CASTINGS IN VAHIOTJS METALS 



Metal 


Shrinkage Allowance in Inches 
per foot length 


and Iron 




1/10 or 0-1000 


letal 


. 


1/8 


0-1250 


i 




. 


3/16 


0-1875 








6/16 


0-3125 








6/16 


0-3125 








1/4 


0-2500 


3T 




3/16 


0-1875 


nth 


. 


5/32 


0-1563 


able Iron 


1/8 


0-1250 


i-mirm . . 


1/5 


0-2000 



See also Patternmaking and Foundryutork, by Ben Show 
ames Edgar, Pitman's Technical Primer Series, 2a. 6d each 



36 WORKSHOP GAUGES 

The use of shrinkage rules enables a pattern to 
be made to the dimensions given on a drawing for 
a finished casting and yet to be just the right amount 
larger in every direction to allow for the difference 
in size between the mould and the resultant casting. 
They save the pattern maker the time required 
otherwise for numerous calculations and allowances, 
and eliminate the nsk of error in such calculations 

Shrinkage rules are generally procurable in English 
measurement in lengths of 6, 12, and 24 inches, with 
shrink allowances per foot varying from ^gin. up 
to -/jj-in. In metric standard they are obtainable 
up to a length of 30 centimetres, with shrink allow- 
ances equivalent to those given above. 

Precautions with Shrink Rules. 

To avoid any possible misuse or mistake, shrinkage 
rules should always be distinctly marked in the 
clearest possible manner to the effect that they are 
shrink rules, and as to the amount of shrink allowed, 
thus 

SHBIKK 1/8" to foot 

or 

1:96 

They should always be kept under lock and key 
in the particular place (e.g pattern shop) where 
they are to be used, and on no account should 
they ever be allowed in a machine shop. 

Steel Tapes. 

For correct measurement of long lengths the 
steel measuring tape is a most useful appliance. 



SIMPLE MEASUREMENT 37 

38 of woven material cannot be depended upon 
rork where real accuracy is required, since they 
liable to stretch with use and to stretch or 
ik with varying atmospheric conditions. Steel 
auring tapes are obtainable in great variety, 
ing in length from 3 feet up to 100 feet. The 
fcer lengths of from 3 feet up to 36 feet are those 
) commonly employed hi engineering practice, 
le tape itself, of these measures, is usually of 
flexible steel strip, finished with a black 
i,ce on which the figures and graduation marks 
larried in a bright finish, so that they are easily 
able against the black background. The steel 
is usually from J to f inch hi width, 
useful form of measure for the shorter lengths 
the steel tape wound on a spring-controlled 
: contained in a flat circular metal case (Fig. 6). 
?e the length of tape required is pulled out and 
anted from being drawn back into the case 
L the tension is removed by a simple automatic 
tet on the spring-controlled drum. When the 
lurement has been completed the ratchet 
tanism is released by a push button and the 
is automatically rewound. 
3el tapes as usually obtained, are graduated 
r in feet, inches and eighths of an inch, or in 
es, centimetres and millimetres. Where the 
io system is used, it is generally the practice 
'aduate the first 10 centimetres in millimetres 
the remainder of the tape in centimetres and 
es. A variety of other graduations can be ob- 
d for special purposes, e.g. architects, builders, 



38 WORKSHOP GAUGES 

surveyors, etc. Steel tapes with British standard 
measurement on one side and with metric measure- 
ment on the reverse are also obtainable (see Fig. 6). 

The Vernier. 

In the measurement of length by means of a 
scale, difficulty sometimes occurs in reading frac- 




J Ohesterman A Co., Ltd 

Fict. 6 STEEL TAPE MOUNTED ON SPUING- CONTROLLED 

DRUM EN METAL CASH. 
The tape Illustrated Ms four scales, two on each side 

tional parts of the smallest division on the scale 
or in reading off accurately the precise dimension 
indicated on the scale. It is, of course, quite 
possible to graduate a division of one inch into as 
many as one hundred equal parts, and to do this 
with a high degree of accuracy. With a scale of 
this type it is theoretically possible to read off 



SIMPLE MBASTIBBMENT 39 



agth accurately to yj^th of an inch, but the en- 
red lines showing each division are very close 
jther and it is not always easy to distinguish 
n or to obtain a result free from inaccuracies. 
eady means of reading accurately with the 
imum possibility of error is provided in what 
nown as the vernier a device owing its origin 
'lerre Vernier, who invented it in 1631. 
ypical caliper gauges with verniers are illustrated 
i'igs. 8 to 11, and the method of reading tho 
tier may be explained by reference to Fig 7. 
r ith very few exceptions, n divisions on the 
ler are made equal to (n 1) divisions on the 
i scale. Then if s be the length of one main 
) division, and v be the length of one vernier 
don, we have, n X v = (n- 1) x s, or v = 
1) s/n Now the smallest possible reading on 
vernier equals the difference between one 
lion on the main scale and one division on the 
ier, i.e. s - v. This reading is called the " least 
t " of the vernier, and, substituting the above 
B for v, we have 

Least count = s-v 



Fig. 7, 25 divisions on the vernier = 24 divi- 

on the main scale. The main scale (which is 

TL larger than full size, for clearness) measures 

)s and fortieths of an inch ; hence s = -fa or 

> in., and n = 25. The " least count " is 

(5383) 



40 



WORKSHOP GAUGES 



therefore 0-025/25 = 0-001, or l-1000th of an 
inch. 

Reading first on the main scale up to the zero 
point on the vernier, we find that the measurement 
illustrated m Fig 7 is 1" + &" + T V + a fraction 
of -jV' i.e. 1-325" + a fraction which is read on the 
vernier. The fraction in question is yjft,/, for the 
fourth vernier line coincides with one of the main 
scale lines, and each vernier division equals 1/1000 in. 



10 15 20 25 



FIG. 7. ILLUSTRATING METHOD OB* BEADING 

THE VUBNTHS. 
The measurement In the case illustrated Is 1 320 in. 

The complete reading is therefore 1-325 + 0-004, 
or 1-329 in. 

The rule for reading this particular vernier may 
be summarized thus 

1. Read the numbers of inches, tenths, and com- 
plete fortieths on the main scale up to the zero of 
the vernier. 

2. Note the number of the vernier line (counting 
from zero on the vernier scale) which coincides 
with a line on the main scale, then this is the number 
of thousandths to be added to the main scale 
reading. 

3. When reading internal measurements the 



SIMPLE MBASTTBBMENT 



41 



h of the two jaws must be added to the actual 

ing unless another vernier is provided specially 

nternal measurements. 

>llowing the procedure laid down above, the 

er will see that 

) In Fig. 8, the vernier reads to lOOths of an 

, and the measurement illustrated is 0-8 -f- 0-02 

82 in 




J Ohesterman & Co , Ltd 

10. 8 CAUTEB, GAUGE WITH VEBNIEB READING TO 
100THS OF AN INCH. 

This gauge has an adjustable head which, when worn, can be 
removed, tried, and re-sot 

In Pig. 9, the inch-vernier reads to lOOOths 
n Fig. 7) and the reading is T V" + nftnj-" = 
5 + 0-009 = 0-034". 

In Fig. 9, the centimetre vernier has 26 divi- 

equal to 24 divisions on the main scale. Each 
e main scale divisions equals ^ cm. or 0-06 cm., 
e the vernier reads 0-05/25 or 0-002 cm., i.e. 
m. as its " least count." The reading illustrated 
nm. + mm. = 0-5 + 0-36 = 0-86 mm. 

As a check, the zeros of the inch and centi- 
a scales in Fig. 9 being coincident, and 1 in. 
; 25-4 mm., the metric reading should be 

X the inch reading as obtained at (6), i.e. 




SIMPLE MEASUREMENT 43 

C 0-034 or 0-864 mm., which agrees with the 

obtained at (c). 

example of an angular vernier is shown in 

9 (p 116), and the method of reading it is 

sxplained. 

a full treatment of different types of verniers, 

r numerous examples in the reading of different 

;s on all types of instruments and tools where 

rs are employed, the reader should refer to 

letic for Engineers (2nd edition), by C. B. 



im.* 

ernier caliper reading to 0-001 inch (and not 
ric units) is shown in Pig. 10. 
steel slide rule or" gauge shown in Fig 11 is 
for check measurements on, end measuring 
pin gauges, and the like. It is a highly 
d tool with screw adjustment and verniers 
g to thousandths of an inch or fiftieths of a 
etre. The measurement is taken from the 
led steel plugs (shown in Fig. 11) and both 
al and external readings may be taken. If 
red, flat jaws may be substituted for the plugs. 

nation End-Measuring Bars.' 

s similar to the Standard Reference Bars 
Ded on p. 13, are supplied for workshop use. 
uch service an accuracy of 5 parts in one 
i is ample and is, indeed, higher than has 
to been placed in the workshop for lengths 
40 inches This accuracy represents an error 
3 than one ten-thousandth of an inch in 20 
apman & Hall, 7s 6d. net 



SIMPLE MEASTJREME:NT 45 

33 in terms of the Imperial Standard Yard. 

ier accuracy can be obtained if required, at 

3r cost. 

set of such bars of sizes, in inches, 32, 23, 15, 
6, 5, 4, 3, 2, and two 1-inch bars, will give all 
from 2 to 39 inches advancing by single inches, 

ombinations of two bars only, which are con- 

jd by a simple screw joint. The joints are 




Fitter G'auye As Precision Tool Co , Ltd 

FIG. 12. WOBKSHOP COMBINATION END BAB AND 
AOOHSSOBIES SHOWN DISMANTLED 

ided at one end only, so that the composite 
las always two flat and parallel end measuring- 
i to which slip gauges (p. 79) can be added by 
is of simple extension collets. A typical com- 
tion end bar and accessories is shown in Fig. 
nd it may be mentioned that the twelve bars 
aerated above, together with a 36-piece set 
ip and block gauges, gives more than 380,000 
sizes. They provide a means of applying size, 
jtly to work in operation, in a manner which is 
>ssible by any other known means with the same 
ee of accuracy. 




OT MBASUBBMENT 



IN very many instances it is not possible to measure 
off or to check the dimension of a part by direct 
application of the rule. It then becomes necessary 
to use some instrument which will gauge accurately 
the dimensions of the part to be measured, and to 
check this measurement against a standard rule. 
In other cases where a comparison of dimensions 
is being made against a dimensioned drawing or 
a standard pattern to which the finished part is 
to conform, it is necessary to check from time to 
time the progress of the work. The measuring 
appliances most commonly used in this way are 
various kinds of calipers and standard limit gauges. 

Calipers. 

In many Classes of work, sufficient accuracy is 
obtained by judging by the eye the position of the 
point to be measured in relation to the graduation 
of the instrument (e.g scale). It is, however, not 
always convenient or possible to place the edge of 
the rule in the required position, or to read the scale 
accurately when it is in such a position , for such 
purposes measuring instruments having two points 
of contact are necessary. In certain of these 
instruments scales are incorporated which show 
directly the precise dimension between the two 
points of contact, and in others the dimension is 

46 



INDIRECT MEASUREMENT 47 

obtained on the instrument and the distance 
of the points is then determined, either by 
arison with a standard scale or by checking 
st a pattern or the like. Instruments of the 
>r class include the usual forms of slide calipers, 
t and depth gauges- in the latter class are 
led the various types of ordinary calipers 
Dth inside and outside measurement. 




a 

J Chesterman A Co , Ltd 

13. SIMPLE CALIPER GAUGE, DIVIDED INTO 32iros 
OF AN INCH AND HALF-MILLIMETRES 

he screw for fastening the sliding jaw cannot become detached 
from the gauge 

Calipers. 

th these instruments one point of contact is 
ally fixed and the other is adjustable In use 
xed point is placed against one surface and the 
table point is brought up against the other 
3e. The distance apart of the two points of 
.ct is read directly on the scale incorporated 
e instrument.* Instruments of this type are 
ally procurable in lengths of from 6 to 12 inches 
rom 15 to 30 centimetres 

any forms of slide calipers have a depth gauge incorporated 
hem and carry both a British and a metric scale. 



INDIRECT MEASUREMENT 49 

\ simple form of slide caliper gauge is shown in 
;. 13, and a larger instrument of the same general 
)e is shown in Fig. 14. In the latter case the 
itish scale reads up to 9 inches by 32nds of our 
h, and the metric scale up to 23 centimetres 
prox.) by haK-millimetres. The movable contact 
i be looked in position, when the instrument is 





Brown & Sharp e Mfg Co 

Fio 16 FIRM-JOINT CALIPERS FOB. OUTSIDE (LEFT) 
AND INSIDE (RIGHT) MEASURHMENTS. 

lusted to the desired dimension, by means of the 
mp or locking screw seen at the top of the frame 
which the movable contact piece is carried. 
\. more elaborate form of slide caliper is shown 
Fig. 9 (p. 42). Inside and outside measuring 
ints are provided ; the sliding jaw can be locked 
any desired position by means of the clamp, and 
>at nicety of adjustment of the contact points 
obtained by the micrometer screw adjustment, 
rniers are provided on both the British and the 
trie scales, the British scale reading to l/1000th 



50 WORKSHOP GAUGES 

inch and the metric scale to l/60th millimetre. The 
method of reading the verniers is explained on 
p. 39. 

Inside and Outside Calipers. 

Typical examples of reliable forms of inside and 
outside calipers for ordinary work are shown in 
Fig. 15. The legs are of tempered steel, the 
stud at their junction being provided with a 
thread which screws into the washer. The washer 
is secured by means of flats engaging with a corre- 
sponding hole in the leg. This method of making 
the joint on which the legs move ensures a constant 
degree of friction the amount of which can be varied 
by the user to suit his individual requirements. 

Calipers of this type are normally supplied with 
narrow points, but for special purposes broad points 
are obtainable. Narrow points are more useful 
for a greater range of work. Outside calipers of 
the ordinary form are procurable in sizes of from 
3 inches up to 36 inches: inside calipers of this 
type are not usually made in sizes over 24 inches. 

A second form of inside and outside calipers 
combined in one instrument is shown in Pig. 19. 
This type of instrument is particularly useful for 
small work, and is made in various sizes up to 
8 inches. 

In using calipers, as, for instance, in determining 
the diameter of a cylindrical piece of work with 
outside calipers, or the bore of a cylinder with inside 
calipers, considerable care is required, since instru- 
ments of this class are easily strained and rendered 



INDIRECT MEASUREMENT 51 

Less for very accurate work. Calipers should 
er be applied to gauge the diameter of a piece 
rork whilst it is revolving in a lathe or in any other 
ihine tool ; the legs of a caliper can be sprung 
rt by the exercise of only a moderate amount of 
IQ and measurements taken from moving parts 

frequently inaccurate and misleading, 
aside and outside calipers should be opened by 
Ling the legs apart until the points are separated. 

final adjustments must be made by gentle 
ping of the inside or the outside of the leg against 
le hard surface until the distance apart of the 
its exactly coincides with the required dimension, 
ticular care must be taken that the tapping is 

taken on the contact points 
n reading off the distance apart of the points 
i caliper, a good method, where practicable, is 
place one point on a truly accurate plane sur- 
}, e.g a surface plate. The scale is then placed 
tical to the surface and the measurement made 
the scale with the observer's eye at right angles 
ihe scale. Lack of care in checking the dimen- 
i of a caliper reading may easily result in 
siderable inaccuracy of work 

ing Calipers. 

^or use where great accuracy is required spring 
pers are frequently employed. Typical exam- 
3 of this type of instrument are shown in Fig 
Instruments of this class can be set with great 
uracy and considerable rapidity to any desired 
lensions within their range. They are generally 



52 WORKSHOP GAUGES 

obtainable in sizes of from 3 up to 6 inches radius 
of leg. 

Inside calipers of this type are particularly useful 
as transfer calipers for use in any chambered cavity, 
since after being set exactly to the desired dimen- 
sion they can be withdrawn by springing back the 
legs ; on being released after withdrawal they 
return to their original setting and show exactly 
the size which has been calipered. 





Brown <fc Sharps Mfg. Co 

FIG 16. OTJTSEDB (LEFT) AND INSIDE (RIGHT) 
SPRING CAUPEBS. 

A special form of calipers of the spring type, 
known as tool makers' calipers, resemble those 
shown in Fig. 16 except that the legs are made from 
round bar drawn down and are especially tough and 
of rigid construction. The stud, screw thread, and 
all parts subject to wear are hardened. This type 
is usually procurable in sizes of from 2 to 6 inches 
radius of leg. 

Many other forms of calipers are made and retailed 



INDIRECT MEASUREMENT 53 

pecial purposes, the great number of which 
ide specific mention. There are, however, 
r special features of certain types of calipers 
i may be mentioned briefly. 





L S Starrett Co , Ltd L S. Starrett Co , Ltd 

IG. 17. OUTSIDE CAUPHRS WITH. FIG. 18 INSIDE 
SOBHIW ADJUSTMBNT CAXJFHBS WITH 

SCTRBW ADJUST- 
MENT. 

ff Adjusting Calipers. 

>r large scale work it is not generally possible 
tilize calipers of the spring type and in some 
j the accuracy possible with the ordinary type 
lipers, such as are illustrated in Figs. 16 and 16, 
t sufficientf In such oases a very useful device 



54 



WORKSHOP GAUGES 



is provided in the screw-adjusting calipers shown in 
Pigs. 17 and 18. With these instruments the correct 
setting is obtained approximately by the ordinary 
method and final adjustment is made by the fine 





L S Stamtt Co , Ltd 
FlG. 19 COMBrBTHID 

DIVIDERS, INSIDE AND 
OUTSIDE CALDPEBS 



L 3 btarrett Co , Lt~ 

FIG. 20 REVEBSIBLB 

INSIDE AND OUTSIDE 

CALTPEBS WITH SCREW 

ADJUSTMENT 



adjustment screw on one leg. By this means the 
calipers can be adjusted with very great accuracy 
to any required setting, either for comparison 
purposes or for checking against any required 
dimension. They are obtainable in sizes of from 
4 inches up to a maximum of 36 inches. 



INDIRECT MEASUREMENT 55 

uble calipers, such as are illustrated in Figs. 
id 20, are useful tools, combining the advan- 

of dividers and of both inside and outside 
>rs They are usually sold in 6 and 8 inch 
only, and, for special purposes, have the fine 

adjustment shown in Fig. 20 





rown d> Sharpe Mfy Co Brown & Sharps Mjg Co , Ltd 

. 21 FIRM-JOINT FIG. 22 KEYWAY 

WHRODITB CAT.TPBBS SPRING CALIPERS. 

aphrodite Calipers. 

so are largely used for finding the centre of 
or for testing the accuracy of a centre already 
d. In this form of calipers one leg is similar 
) leg of a compass calipers, and, in the best 
>f the instrument, is provided with a renewable 
; the second leg is the same in principle as 
of an ordinary calipers. When used to 
le centre of a cylinder or of a hole, the bore 
cylinder or hole must bo plugged before tho 
phrodite calipers are applied. 

383) 



56 WORKSHOP GAUGES 

A typical instrument of this class is shown in 
Pig. 21, in which the needle point is adjustable by 
means of the thumb screw in the leg. This allows 
for wear on the point. Such calipers are usually 
obtainable in sizes of from 4 up to 10 inches radius 
of leg. 

Keyway Calipers. 

Another useful special type of calipers is the 
keyway or keyhole spring-type instrument shown in 
Fig. 22. 

Special Types of Inside Calipers. 

For inside measurements where the distance 
between two points is too great or too inconvenient 
for the extent to which ordinary inside calipers 
can be used, an instrument is sometimes employed 
which consists essentially of two legs held together 
by screws threaded into nuts. The screws are 
formed with shoulders fitting into the slots on 
the two legs which form guides on which the legs 
move. The nuts on the screws are set so as to 
bind the legs together, but to allow them to move 
slightly in relation to one another when either end 
of the legs, remote from the points, is struck by a 
light tapping. When the points are adjusted to 
their exact dimension required, the locking screws 
are firmly fixed home. 

An instrument of this type is often accurate 
enough for ordinary work, but where extreme 



INDIRECT MEASUREMENT 57 

,cy is required special types of inside calipers 
metimes employed. These generally consist 
1 tubes telescoping the one into the other and 
ig at one end either a one-inch or a 25-milli- 
micrometer screw movement. With this 
)f instrument measurement can be carried 
er a range of from 30 to over 100 inches or 
uivalent in millimetres, with an accuracy of 
th inch, or l/100th millimetre. 

i or Screw Fitch Gauges. 

principal thread systems used in Great 
L are the Whitworth form of thread and the 
Association thread. These systems are 
lly abbreviated and are known as the B.S.W. 
e B.A. threads. Whitworth thread propor- 
re much used on the continent to millimetre 
ions ; other threads in use on the continent 
ie De Lisle, the Systeme Internationale, 
he Thury. The United States standard 

is largely used throughout America and 
L. 

Whitworth form of thread is defined by the 
Engineering Standards Association* as 



Thitworth form of thread is one in which the angle 
the flanks, measured in the axial plane, is 55 ; one- 
the sharp triangle is truncated at top and bottom, the 
Deing rounded 'equally at crests and roots to a radius 
therefore 0-137329 times the pitch ; the depth of the 
0-640327 times the pitch. 



acation O.L. (M) 7270, June, 1910. 




58 WORKSHOP GAUGES 

The British Association form of thread is defined 
by the British Engineering Standards Association* 
as follows 



Tho British Association form of thread is one in which the 
angle between the flanks, measured in the axial plane, is 47-0 ; 
tha threads are rounded equally at crests and roots to a radius 
of nearly two-elevenths of the pitch, leaving the depths of 
threads given in Table I.f 



The United States standard thread (known 
also as the Sellers, or Franklin Institute Thread) 
has an angle between the flanks of 60 with flat 
crest and roots. 

It is frequently necessary to determine the pitch 
of a screw or of a threaded piece of work ; this can 
readily be determined by the use of screw pitch 
guages, typical examples of a gauge of this type 
being shown in Figs. 23 and 24. The instrument 
consists of a series of leaves carrying standard 
thread pitches ; the standard of each leaf is clearly 
stamped or engraved on the face of the leaf and the 
leaves are hinged at one end to fold into a case when 
not in use. The thread system with which the 
gauge complies (e.g British Standard Whitworth, 
British Association) is engraved or stamped on the 
case 

In use the thread system is first determined by 
examination ; various leaves of the gauge are then 
placed successively over the thread until one loaf 
is found to coincide with tho thread ; the pitch is 

* Publication C.L. (M) 7271, June 1919 

t Soo page 12 of Publication C.L. (M) 7271, June, 1919. 




L S Starrett Co , Ltd 

t 23 SCREW PITCH GAUGE, SHOWING THREADS 
PER INCH AND DOUBLE DEPTH or THBEAD 




J Chesterman & Co , Ltd 

24 WHITWORTII STANDARD SCREW PITCH 
GAUGE 



60 WORKSHOP GAUGES 

then read off from the number engraved or stamped 
on this particular leaf 

Gauges of this type are generally obtainable in 
British and metric standards for all thread systems, 
and are made up with from 20 to 30 pitches of vary- 
ing standards ranging from 4 down to 80 pitches 
per inch. 

The free end of each leaf (Fig. 23) is made narrow 
to enter a small hole or nut, so that internal as well 
as external threads can be gauged. The first 
number on each blade is the number of threads 
per inch. 

The second (decimal) number stamped on each 
leaf is the double depth of the thread to which that 
leaf corresponds. The use of this number is as 
follows: When a hole is to be tapped, measure the 
diameter of the tap over the threads by a micrometer 
and deduct the decimal number given on the gauge 
leaf which agrees with the pitch of the tap. The 
result gives the diameter of drill to be used if a full 
thread is to be cut. If the thread is to be not full 
but flattened, allowance must be made for the 
amount by which it is to be flattened. 

The screw pitch is sufficiently accurate for ordinary 
workshop use, but special methods must be employed 
for the measurement or checking of screw gauges, 
lead screws, and other threads in which a very high 
degree of accuracy is required. For a full treatment 
of the theory and practice of precision measure- 
ments on screw threads, the reader may be refer- 
red to publications issued by the National Physical 
Laboratory (see Bibliography, p. 148). 



INDIRECT MEASUREMENT 61 

Gauges. 

iere a number of measurements of the diameters 
3tal, -wire, or rod have to be made, it is often 
snient to use one or other of the numerous 
3 of notched steel gauges now universally 
nable. In this type of gauge, the widths of 
lotches are equal to the recognized standards, 
are numbered so that by reference to a table 
liameter of any wire or rod corresponding to 
en gauge number can be readily ascertained, 
aples of two well-known forms of this type of 
B are given in Figs. 25 and 26. Generally, a 

of wire gauge numbers and the corresponding 
eters of wire is stamped on the back of the 
B plate. 

should be noted that gauges of this type, i.e. 
ig notches, are not suitable for the accurate 
urement of sheet metal, since the edges of such 
>s frequently vary from the thickness of the 

of the sheet. 

tien gauges of this type are used they are 
red to slip over the thickness of the metal 
B measured and the consequent friction and 
ing tend to cause a minute enlargement of the 
i ; their accuracy is, therefore, gradually 
oyed. It is also a disadvantage that they will 
Letermine thicknesses intermediate between any 
gauge numbers. The micrometer caliper (p. 
s not subject to this limitation and can be 
jted to compensate for wear, 
e thickness corresponding to a given wire 
e number varies according to the system 




L S Starrett Co., Ltd 
FIG. 25 IMPERIAL STANDARD WIRE GAUGES. 




L S Starrett Co , Ltd 
PIG. 26. IMPERIAL STANDARD WIRE GAUGES. 



INDIRECT MEASUREMENT 63 

ning the numbering of the gauge, and also 
the class of metal or wire for which the gauge 
een constructed . For ordinary work throughout 
b Britain the Imperial Standard and the 
ingham (also known as the Stubbs) wire 
as are those most frequently employed ; see 
ss XII and XIII. 

gauge system in common use throughout the 
jd States is the American Standard, which is 
mown as the Brown and Sharpe Gauge (Table 
i. In this system the value of 0-46 in. has been 
i as the thickness corresponding to the largest 
osion of the gauge ; each of the 43 successive 
between 0000 (or 4/0) and 40 gauge is decreased 
uniform decrement, namely by multiplying its 
>cessor by 0-890522. The value for B. & S. 
3 number 36 ifi 0-005 in., which corresponds with 
>er 35 on the Birmingham wire gauge, 
e advantages of the United States system is 

the gauges are easier to produce than those 
Ducted to a scale in which each figure does 
aear a proportionate value to the preceding 
) ; the difference between any two gauge 
)ers in the B. & S. series is easily found by 
lation. 

rious other standards are in use for special 
Dses ; such as those for sheet iron (Table XV), 
msic wire, for rolled sheets of silver and gold, 
heet zinc, and for numerous other purposes, 
workshop mechanic in this country is, how- 

mainly concerned with the Standard and the 

ingham wire gauges. 



64 



WORKSHOP GAUGES 



TABLE XH 

IMPERIAL STANDARD WIBHJ GAUGE 



Descrip- 
tive 
number 


Equivalent 
in parts of 
an inch 


Metric 
equivalent 

nrm 


Sectional area of wire 


Square in 


Square 
mm 


7/0 


600 


12700 


1963 


126-67 


6/0 


464 


11-786 


1691 


10909 


6/0 


432 


10973 


1466 


94-56 


4/0 


400 


10160 


1257 


81-07 


3/0 


372 


9-449 


1087 


7012 


2/0 


348 


8-839 


0951 


61-36 





324 


8-229 


0824 


53 19 


1 


300 


7-620 


0707 


4560 


2 


276 


7-010 


0598 


38-58 


3 


252 


6-401 


0499 


32-18 


4 


232 


5-893 


0423 


2727 


5 


212 


5-386 


0353 


2277 


6 


192 


4877 


0289 


18 68 


7 


176 


4-470 


0243 


1570 


8 


160 


4-064 


0201 


12-97 


9 


144 


3-658 


0163 


10-61 


" 10 


128 


3-251 


0129 


830 


11 


116 


2-946 


0106 


682 


12 


.104 


2642 


00849 


548 


13 


092 


2-337 


00665 


4-29 


14 


080 


2-032 


00503 


3-24 


15 


072 


1 829 


00407 


2-63 


16 


064 


1 626 


00322 


2-07 


17 


056 


1-422 


00246 


1-59 


18 


048 


1-219 


00181 


1-17 


19 


040 


1 016 


00126 


811 


20 


036 


914 


00102 


657 


21 


032 


813 


00804 


519 


22 


028 


711 


000616 


397 


23 


024 


610 


000462 


292 


24 


022 


559 


000380 


245 


25 


020 


508 


000314 


203 


26 


018 


457 


000264 


164 


27 


0164 


4166 


000211 


136 


28 


0148 


3759 


000173 


111 


29 


0136 


3454 


000145 


0937 


30 


0124 


3160 


000121 


0779 


31 


0116 


2946 


000106 


0682 



INDIRECT MEASUREMENT 



65 



TABLE XII (continued) 



irip- 

e 
ber 


Equivalent 
in parts of 
an inoh 


Metric 
equivalent 

mm 


Sectional area of wire 


Square in. 


Square 

mm. 


j 


0108 


2743 


0000916 


0591 


J 


0100 


2540 


0000786 


0607 


t 


0092 


2337 


0000665 


0429 


5 


0984 


2134 


0000564 


0357 


} 


0076 


1930 


0000464 


0293 


1 


0068 


1727 


0000363 


0234 


J 


0069 


1624 


0000283 


0182 


) 


0052 


1321 


0000212 


0137 


) 


0048 


1219 


0000181 


0187 


L 


0044 


1118 


0000152 


00982 


j 


0040 


1016 


0000126 


00811 


J 


0036 


0914 


0000102 


00666 


t 


0032 


0813 


00000804 


00619 


5 


0028 


0711 


00000616 


00397 


J 


0024 


0610 


00000462 


00292 


1 


0020 


0508 


00000314 


00203 


3 


0016 


0406 


00000201 


00129 


) 


0012 


0305 


00000113 


00073 


) 


0010 


0254 


000000785 


00051 



TABLE XIII 
(STTTBBS) WIRE 










ID 




g M 




d m 

1* 


II 


9 0) 


f 1 ! 


a CO 
(D 


ll 


H (D 


S o 














m a 


S a 


os 9 


<B d 


oa -a 


<D 


OQ y 




ft 




ft 




fl 




464 


7 


180 


17 


068 


27 


016 


425 


8 


165 


18 


049 


28 


014 


380 


9 


148 


19 


042 


29 


013 


340 


10 


134 


20 


036 


30 


012 


300 


11 


120 


21 


032 


31 


010 


284 


12 


109 


22 


028 


32 


009 


259 


13 


095 


23 


025 


33 


008 


238 


14 


083 


24 


022 


34 


007 


220 


15 


072 


25 


020 


35 


005 


203 


16 


065 


26 


018 


36 


004 



66 WORKSHOP GAUGES 

TABLE XIV 
AMERICAN (BROWN & SHARPE) WIRE GAU 








<D 




a> 







> ^ 




^ . 




^ 






> ID 


S 


<D 


3 23 


-S 0) 


3 $ 


-Ja 9 


2"n 





ftja 


Jj 


ft^ 




& 1 F 


t) a 





2 1 


S u 


h S 


S "" 


8 E 


d 


OQ -3 


$ fl 


<n S 


d 


ra 3 


S S 


fl 




fl 




fi 




Q 


4/0 


4600 


8 


1285 


19 


0359 


30 


3/0 


4096 


9 


1144 


20 


0320 


31 


2/0 


3648 


10 


1019 


21 


0285 


32 





3249 


11 


0907 


22 


0253 


33 


1 


2893 


12 


0808 


23 


0226 


34 


2 


2576 


13 


0720 


24 


0201 


35 


3 


2294 


14 


0641 


25 


0179 


36 


4 


2043 


15 


0571 


26 


0159 


37 


5 


1819 


16 


0508 


27 


0142 


38 


6 


1620 


17 


0453 


28 


0126 


30 


7 


1443 


18 


0403 


29 


0113 


40 



TABLE XV 
BIRMINGHAM SHEET IRON GAUGE 



Descrip- 
tive 
number 


Size in 
Inches 


Descrip- 
tive 
number 


Size in 
Inches 


Descrip- 
tive 
number 


1 


3125 


12 


1125 


23 


2 


28125 


13 


10 


24 


3 


25 


14 


0875 


25 


4 


234375 


15 


075 


26 


5 


21876 


16 


0625 


27 


6 


203125 


17 


05625 


28 


7 


1876 


18 


05 


29 


8 


171875 


19 


04375 


30 


9 


15625 


20 


0376 


31 


10 


140625 


21 


034375 


32 


11 


125 


22 


03126 





INDIRECT MEASUREMENT 



67 



kness or Feeler Gauges. 

L many cases of assembly and fitting work, 
in numerous other instances, it is frequently 
ired to determine the distance apart of two 
il surfaces or the degree of approximation of 
surfaces to one another. It is not always possible 
scertain this dimension by direct measurement 




Fio 



J Chesterman & Co 
27. FBEUER OB THICKNESS GAUGE. 



Ltd 



j the use of inside calipers, particularly where 
dimension concerned is very small, and in work 
.his class thickness or " feeler " gauges are 
uently employed 

seler gauges are usually made up in leaves 
ed together at one end and folding into a con- 
ent case. The leaves are usually from 3 to 4 in. 

by \ in wide, being either parallel throughout 
p length or tapering towards their free ends. 

number of leaves in a set range normally from 



68 WORKSHOP GATJGES 

6 to 10, and vary in thickness from 0-0015 up to 
0-025 in. in British, standard measurement and 
from 0-05 millimetre upwards in the metric system. 
A typical feeler gauge is shown in Fig. 27. The 
thickness in thousandths of an inch or in hundredths 
of a millimetre is engraved clearly on each leaf , 
leaves may be used singly or in combination with 
other leaves and any thickness within the limits of 
the various combinations permissible, can readily 
be determined by trial and error. 

Plug and Ring (or Collar) Gauges. 

Gauges of this type provide standards of diameter 
for general workshop use ; as generally supplied 
for ordinary workshop use they provide a limit of 
accuracy within l/500th part of an inch A typical 
set of such plugs and gauges is shown in Fig. 28 , 
the diameter of the plugs and the bores of the rings 
generally advance by -fa in. from ^ to 2 ins., by 
$ in. from 2 to 4 ins , and by in. from 4 to 8 in , 
or by similar increments in metric measure. The 
gauges are of hardened steel, lapped to size, and 
they are applied to the work in course of manufacture 
or to the finished piece in order to ascertain whether 
the diameter of a hole (tested by the plug gauge), 
or of a turned spindle, etc. (tested by the ring gauge), 
is or is not equal to that of the gauge. There is no 
means of determining by these gauges the magnitude 
of any difference between the diameters of the gauges 
and of the work, but an experienced workman can 
estimate the difference approximately by the " feel " 
of the next smaller plug or next larger ring, as the 



INDIRECT MEASUREMENT 69 

may be. There are available plug and ring 
33 of diameters corresponding to various 
js of fit e.g. force, driving, push, and running 
on or in different nominal diameters. These 
38 are very useful for the inspection of machine 
onenta prior to assembly. 




J Ackworttne, Ltd 

7 iG. 28. TYPICAL SET OF PT.ATN" PLUO AND Rnra 
GAUGES. 

ien the work is very near to the size of the 
>, a plug gauge may be forced into (or a collar 
> may be forced over) the work, but this should 
be done. A plug gauge should never be 
>d into a hole, or a ring gauge over a spindle, 
will not go without appreciable friction or 
ance. If the size of the work is correct, the 
s will fit without perceptible play. 




J Ac 
FIG. 29 " Go " AND " NOT Go " PLUG 




Newall J 
Fro. 30. NEWALL INTERNAL LIMIT GA 

CLASS "A" 

The long end IB the " go " end which enters tho hoi 
short end is the " not go " which must not en 





Brown <t Sharps Mfg. Co 

ha 31. EXTERNAL (LEFT) AND INTERNAL (BIGHT) 
LIMIT GAUGES. 

Vote the differently shaped ends, which facilitate Identification 
if the larger and smaller ends without reference to the sizes 
stamped thereon 




Brown & Storpe Mfg Co 

G. 32. STANDARD CAUFER GAUGES TOR EVERYDAY 
WORKSHOP USE. See also FIG. 33. 

towing double-ended, external and Internal pattern (right) ; 
also single-ended gauges (centre and left) 

5383) 



72 WORKSHOP GAUGES 

Limit Gauges. 

A gauge of a very useful type, known as the 
" limit gauge," is shown in Figs. 29 to 31. With 
this type of gauge two fixed dimensions are provided, 
one being the "go" and the other the "not go." 
In use, the diameter to be gauged is to be such that 
the " go " dimension of the gauge will just slip over 




Brown <& Shaiye Mfg Co 

FKJ 33 STANDARD CAMPER GAUGES, SHOWING CoNSTB.ua- 
TION ADOPTED FOR LARGER SIZES. (Of. FIG 32). 

or inside the work, and the " not go " dimension 
will not enter or pass over the work. As the 
difference between t|ie two dimensions provided by 
the gauge may be extremely minute, it follows that 
work passed by this gauge can be made accurate 
to a very high degree. The actual difference 
between the "go " and " not go " diameters depends 
upon the " tolerance " allowed in the dimensions 
of the work to be checked (see Chapter VII) 

Limit gauges are generally procurable in sizes 
ranging from J in up to 6 in. Adjustable gauges 



INDIRECT MEASUREMENT 73 

is type are also obtainable in which the precise 
nsions of the " limits " can be varied within 
,m narrow limits. With this type of limit 
e the same instrument can be used for varying 
nsions of work and the extent of permissible 
,tion of the work can also be altered at will. 




/ AcktvorlJne, Lid 

FIQ 34. ADJUSTABLE PLAIN CALIPBR GATTGE, 
HIGH AND Low LIMIT 

stable Caliper Gauges. 

16 ordinary type of limit gauge for outside work 
ot be adjusted for wear, and provides only one 
3 of permissible error (corresponding to the 
*ence between the " go " and " not go " 
eters). With this type of gauge the " go " 
inevitably becomes worn with use and its 



74 WORKSHOP GAUGES 

accuracy is thus lost ; wear on the " not go " end 
of the gauge is negligible. In use, therefore, this 
type of gauge permits an ever-increasing error, 




NeiaaU Engineering Co 

FIG. 35. NEWALL ADJUSTABLE EXTERNAL LIMIT 

GAUGE. 

Provided with two palra of anvils which are quickly adjusted 
to the diameter and class of fit required 

and though the rate of wear may be very slow, the 
gauge must ultimately become useless for accurate 
work and has to be scrapped. 

A useful form of adjustable oaliper gauge is 
shown in Fig. 34. The body is of malleable iron ; 



LOCKING SOfEW 



ADJUSTING SCREW 




rfO HOLES FDR 
1G SPANNER 



SLOT FOR PEG 
SPftMNER 

.dZ/red Hert-ert, Ltd. 



36 SHOWINO THE CONSTRUCTION OF THE WICKMAN 
CAUPEB GATTGE WITH THHJBADBJD 



76 WORKSHOP GAUGES 

a special key is provided for the adjustment of the 
anvils, and the construction is such that adjustment 
can only be carried out by this means. The adjust- 
ing screws do not project from the body portion 
whatever the diameter to which the gauge is set 
to measure. This gauge is made in 18 sizes with 
a range of adjustment varying from to in. up 
to 15 or 16 in. A larger adjustable gauge of the 
same general construction is shown in Fig. 35. 

The adjustable Wickman caliper gauge is shown 
in Fig. 36. The tool illustrated is for gauging screws 
and other externally threaded work. The " go " 
anvils have full form threads ; they ensure that 
the diameter of the screw is not too large and, being 
of sufficient width to give the required length of 
engagement, they also check the pitch. The " not 
go " (inner) anvils have only one or two threads, 
and these are cleared away at the root and at the 
crest, so that the threads come into contact only 
with the effective diameter of the screw, which is 
the element they are intended to control. If the 
pitch error in the screw be too great the effective 
diameter will have to be reduced to such an extent, 
in order to get the screw through the " go " anvils, 
that it will also pass through the " not go " anvils 
and therefore be rejected. 

For the limit gauging of plain (not threaded) 
work, the general construction of the caliper is 
the same, but plain parallel anvils are used. 

When used in combination with renewable-ended 
plug limit gauges this gauge is an ideal equipment for 
controlling all kinds of shaft and hole work. The 



INDIRECT MEASUREMENT 77 

;e of adjustment on each gauge is Jin. in the 
j up to 1| in., and in. in the larger sizes up 
12 in The fractional difference between the 
" and the "not go " gauges can, of course, be 
/rolled and regulated to any desired extent, 
djustment of the anvils is made as required and 
locking mechanism is covered by a lead seal 
jh can be indented with the users' mark so that 
mauthorized alteration of the seal can escape 
ction. ' 



1 ' '"Illl l'l""'rillTITI'IT' T" 
3 Aau la-^aBJB^. [I "Jf^ 



LiilililililiLliliiilililiiilililililililllllLlililililil'ililililililililililililiiiHiimiliiiliTiliiiiililililllilllilili 



J Chetterman <fc Co , Ltd 

FIG 37. SIMPLE DEPTH GAUGE FOB DIRECT 
BEADING AT END OF SLIDING BAH 

th Gauges. 

There it is necessary to measure with great 
iracy the depth of recesses or holes, as in jig 

die work, depth gauges are of great service. 
ts simplest form, the depth gauge consists of 
eel straight edge with a stout wire held in a 
ve, at nght angles to the axis of the straight 
>, by a milled-headed nut. The depth of the 

or recess to be measured is obtained by setting 
wire and the extent of its projection from the 
ight edge is then ascertained by measurement, 
ither forms of this instrument a graduated scale 
3ed instead of the stout wire, and the depth is 
L off direct on the scale. 



INDIRECT MEASUREMENT 79 

L simple form of depth gauge is shown in Fig. 37 
L a more elaborate design m Fig. 38 . In the latter 
B a total depth of 4 in. can be measured to 
4th in. on one side of the scale and, by means of 

vernier, to lOOOths of an inch on the front of the 
Le. The depth indicated by the gauge in Fig. 
is | in., and that shown by the gauge in Fig. 38 
3-060 in It will be seen that, in Fig. 38, the 
D of the vernier scale is the same distance from 

measuring edge of the gauge as the zero on the 
Le is from the end of the latter , the reading is, 
course, taken on the zero line of the vernier, 
s the vernier reading if any. A micrometer 
ith gauge is illustrated in Fig. 54, p. 98. 

Le and Step Gauges. 

\. gauge of this type is illustrated in Fig 39. 
B feet of the frame are placed on the surface 
m which the depth of hole or height of step is to 
measured, and the slider is set to touch the bottom 
the hole or the top of the step as the case may be. 
e reading on the centre-zero scale then gives, at 
ie, the desired dimension. 

p and Block Gauges. 

\. typical set of these gauges is shown in Fig. 
and a few of their many applications are illus- 
,ted in Figs. 41 to 44. The gauges are made in 
a of eight or multiples of eight, the various pieces 
each set being interchanged during the process 




J Chesterman & Co , Ltd 
FIG. 39 HOLE AND STEP GAUGE 



INDIRECT MEASUREMENT 



81 



mufacture according to a definite programme* 
L ensures that all the pieces progress steadily 
ds an ever-higher degree of accuracy, both 



H J g .H H H M -H H ffl 

H H H B Q 'D ffl Q B 

'^GJtasrjBua-^--^ '...- .-- - 

H Q Q M 'Q H ffl ffl D 



Ptfter Gawi/e <fc Precusion TooZ Co , Ltd. 
FIG. 40. SMALL SET OF SLIP GAUGES 

igards size and parallellism of faces. It is 
ly of remark that the precision now attained 
e manufacture of these gauges and in their 
urement by the " generator comparator " (p. 
, such that the greatest uncertainty in the whole 
i,tion is that involved in detennining the parent 

etailed in a brochure entitled Accuracy in Industry, issued 
3 Fitter Gauge and Precision Tool Co , Ltd , Woolwich, 




Fitter Gauge & Precision Tool Co., Ltd. 

FIG 41 TESTING LIMIT GAUGES BY MEANS OP 
SLIP UAUGES. 




FIG. 42. 



Pitter Gauge <fc Precmon Tool Co., Lid. 
A JIG BY MEANS OF SUP GAUGES 
AND HEIGHT GAUGE. 




Fitter Gauge & Precision Tool Co., Ltd. 

43. HEIGHT GAUGE, 4-nr. JAWS, AND SUP GAUQBS 
SET TIP TO TATTTB A. LENGTH Mm A TTRIC I M"H'.VT I - 




Pitttr tfoufffl db Precision Tool Co , Ltd. 

FIG. 44. SHOWING METHOD OF TESTING A STANDAHD 

CYIJNDBR GAUGE BY MEANS or CAUBBATHD ROLLERS 

AND SLIP GAUGES. 



84 WORKSHOP GAUGES 

end standard in terms of the fundamental line 
standard (the Imperial Yard). Once the parent 
bar is obtained the smaller bars, blocks, and slips 
are accurate subdivisions of the parent standard, 
the initial tolerance on which is distributed pro- 
portionately, according to length, amongst all the 
pieces generated from it. 

Various sets of slip and block gauges are provided 
to meet different requirements, there being from 28 
to 103 pieces in the set according to the increments 
and number of combinations required. A full set 
of English gauges comprises 81 pieces, viz., 9 from 
0-1001 to 0-1009 by ten-thousandths of an inch ; 
49 from 101, by thousandths; 19 from 0-05 to 
0-95 by increments of 0-05 in. ; and the four sizes 
1, 2, 3 and 4 in. 

The use of slip gauges to test limit gauges is 
illustrated by Fig. 41. Slip gauges, used indepen- 
dently and in combination in a height-gauge frame, 
are employed for such purposes as checking jigs 
(Fig 42) The height gauge frame, in conjunction 
with slip gauges and special jaw pieces, offers a 
convenient method of measuring lengths in the 
workshop (Fig. 43). The use of combination end 
bars for the measurement of lengths up to 40 in. 
has already been described (see Fig. 12, p. 45). 
Though rectangular slips will not make face-contact 
with the interior of a ring gauge, the latter may 
be checked by a combination of slip gauges and 
calibrated rollers as shown in Fig. 44. The rollers 
for this purpose are calibrated against shp gauges 
by means of the " generator comparator " (p. 12). 



CHAPTER IV 

MICKOMETERS 

EN a screw is rotated through, one complete 
>lution it moves, in relation to the part threaded 
b (e g. its nut) a distance equal to the " pitch " 
tie screw, or in other words, through the distance 
veen two consecutive turns of the thread. This 
ance is generally a known quantity ; ii the 
tch " is not already known it can be determined 
means of gauges. A number of measuring 
ices are in use in which contact of the points, 
sveen which measurement is made, is effected 
a screw adjustment. 

rometer Calipers. 

nstruments of this class are very extensively 
i in measuring the thickness of plates, diameters 
ods, and for many other purposes For protec- 
i against dirt, grit, and mechanical injury they 
generally supplied in cases as shown in Fig. 
In the usual form of micrometer calipers the 
)h of the screw is made small (generally l/40th 
, and the screw has attached to it a thimble 
dng its circumference divided into a number of 
tal parts (generally 25) The amount of move- 
nt equal to a fraction of a complete revolution 
rotation of the screw can then be determined 
i it is possible to read with great accuracy the 
bance through which the point of the screw, 
85 



86 WORKSHOP GAUGES 

forming one end of the measuring appliance, has 
moved. 

The construction of a simple micrometer caliper 
and the manner of using this instrument may be 
explained by reference to Fig. 46. The spindle 
C is attached to the thimble E on the inside at the 
end, H. That part of the spindle which is con- 
cealed within the sleeve D and thimble E is threaded 




Brown ds Sharps Mfg Co. 

FIG. 46. MIOBOSCBTBR WITH. RATCHET STOP AND 
CT.AMT Rnsro. 

to fit a nut in the frame A. The frame being held 
stationary, the thimble E is revolved by the thumb 
and finger, thus turning the spindle C in its nut, 
and causing C to approach or recede from the anvil 
B. The piece to be measured is placed between 
B and C, and the distance between the faces of the 
anvil and spindle is shown at any moment by the 
lines and figures on the sleeve D and thimble 13.* 



MICROMETERS 



87 



ie pitch of the thread on the concealed part 
xe spindle is -fo in., so that one complete revolu- 

of the thimble increases or decreases the 
mce between anvil and spindle by -fa in. (0-026 

Each division of the scale on D corresponds 
ne turn of the thimble, i.e. to T V or %$$$ in. 



A-FRAME 

B-ANVIL 

C-SPINDLE 

D-SLEEVE 

E-THIMBLE 




L. S Starrett Co , Ltd 
FlO 46. MlOBOMBTBB OALIPEB. READING TO 

1000TH INCH. 

numbers on this scale are four divisions apart, 

therefore indicate T V or 3^ in. The bevelled 

of the thimble is divided eircumferentially 

25 equal parts ; these are read against the 

line of the scale on D, and each division on 

rresponds to l/25th of one turn of E, i.e. to 

h of 0-025 m. or 0-001 in. movement of the 

le towards or away from the anvil. 

the setting illustrated by Fig. 46 the reading 

e micrometer is 1 on scale D (=0-100 in.) 

bhree small divisions on scale D (= 3 X 0-025 

ulna three divisions on the thimble (= 3 X 

in.), or 0-100 -f 0-075 + 0-003 = 0-178 in. 

383) 




MICROMETERS 



89 



?he skeleton view in Fig. 47 shows the internal 
shanism of a Starrett micrometer with: (a) the 
irled locking nut which contracts a split bushing 
nd the spindle, keeping it central and true and 
ang it firm to make a solid gauge if desired ; 
the ratchet head which enables the spindle 




THIMBLE 

cn o 



198765*32 

SLEEVE 



fit) 



es43ai o 

SLEEVE 

(c) 



(a,) 



FIG 48 ILLUSTRATING METHOD OF READING A 
"TEN-THOUSANDTH" MICROMETER CALIPER 

,ys to be tightened on to the work to a uniform 
ee, thus making for accuracy by preventing 
raiation of the work and strain or wear on the 

\ 

>ecial forms of micrometer calipers incorporating 
Additional vernier are obtainable. With this 
of micrometer, ten lines equally spaced apart 
ngraved on the adjustable sleeve which occupy 
same space as nine of the divisions on the 
ble so that the difference of the spaces apart 
3 lines on the sleeve is one-tenth of the distance 
. of the lines on the thimble. The vernier 
fore gives a reading to a further place of 



90 WORKSHOP GAUGES 

decimals or to an accuracy of one ten-thousandth 
of an inch. 

The arrangement of scales on a " ten-thousandth " 
micrometer caliper and the method of reading them 
will be clear from Fig. 48. The illustration a, 
shows the general appearance of the three scales on 
the actual instrument, while 6 and c show the 
" development " of the scales, i.e. their appearance 
if the barrel of the micrometer were cut longitudin- 
ally and laid out flat. In Fig. 486 we have two- 
tenths plus two small divisions on the main scale 
of the sleeve, i.e. 0-2 + (2 x -025) or 0-25 in. ; 
the reading on the thimble is zero and the vernier 
reading is also zero (the lines at each end of the 
vernier being exactly coincident with divisions 
on the thimble) ; the complete reading is, therefore, 
0-2500 in in this case. In Fig. 48c the main scale 
reading is 0-25 in. as before, the thimble reading 
is plus a fraction of one division ; this fraction 
is read on the vernier and is seen to be 7 ten- 
thousandths of an inch (the 7 line on the vernier 
coinciding with one of the divisions on the thimble) , 
the complete reading in this case is therefore 0-25 +' 
(0 X 0-001) + (7 X 0-0001) or 0-2507 in. 

(NOTE. The thimble reading (thousandths of 
an inch) is taken on the axial line of the main scale 
of the sleeve and not opposite the zero of the vernier 
scale ; in other words, the thimble reading in Fig. 
48c is thousandths plus the vernier reading, and 
not 3 thousandths plus the vernier reading.) 

Micrometer calipers of the ordinary form are 
generally procurable to read in British measurement 



MICBOMETBBS ' 91 

i to in., from to 1 in., and from to 2 in. 

netric measurement the usual sizes are from 

13 mm.., to 25 mm., and from to 50 mm. 

riementary Fittings. 

number of ingenious devices ensuring greater 
and accuracy of reading have been introduced 
i time to time ; the more important of these 
be briefly noted. 




Brown A Sharpe Mfg Co 
FIG. 49 DIRECT READING MIOBOMETHB 

ct Beading Micrometer. 

ie micrometer caliper shown in Fig. 49 enables 
sandths of an inch to be read in plain figures 
out the use of a vernier. The figures showing 
ie opening nearest the frame indicate the move- 
fa of the spindle by tenths of an inch. Those 
he next opening register the movement by 
Iredths of an inch, while the figures in the last 
ing indicate the movement by thousandths, 
iddition, the thimble on the end of the sleeve is 
uated in connection with a line on the sleeve 
jad to thousandths of an inch. By means of 



92 WORKSHOP GAUGES 

these lines, fractional parts of a thousandth may be 
estimated. 

The registering mechanism is so constructed that 
the dials are positively locked, and the micrometer 
cannot get out of adjustment and read incorrectly. 
The range of the instrument is up to 1 inch. 

Quick Adjustment Device. 

In using a micrometer caliper of the ordinary 
type it sometimes takes an appreciable time to 
open it the required amount for the particular 
measurement involved and to close it after it has 
been used and is to be put away in its case. Since 
there are 40 threads to the inch, forty complete 
revolutions of the thimble are required for opening 
or closing to an extent of one inch. This operation 
takes, say, 20 seconds, so that, in the course of a 
day, a considerable amount of time may be saved 
by the use of quick adjustment calipers. In these 
instruments it is only necessary to press with the 
finger against the end of the plunger in order to 
release the nut, disengaging it from the screw, and 
allowing any adjustment within the range of the 
calipers to be made instantly. On releasing the 
pressure, the nut engages again with the screw and 
the fine adjustments can then be made in the ordinary 
way. 

Ratchet Stop. 

Micrometer calipers can easily be strained if 
more than a certain amount of pressure be applied 



MIOEOMBTBES 93 

he screw ; possible overstraining is largely 
rnted by the provision of a ratchet stop in 
h. the ratchet slips by the pawl if too great a 
ure be applied. The spindle is thereby pre- 
jd from turning too far and possible springing 
e instrument is avoided. Pig. 47 (p. 88) shows 
ly the construction of this useful attachment, 
levice is particularly applicable when a number 
leasurements have to be taken quickly and 
cularly when the same instrument is used for 
ig measurements by more than one person ; 
ie latter case the same amount of pressure ia 
in each case on the objects being measured. 



)ensation for Wear. 

course of time wear on the screw and nut, on 
nvil, and on the end of the spindle of micrometer 
ers is inevitable. In some cases provision 
,de for this wear by allowing for the adjustment 
le anvil. A more satisfactory method con- 
of the provision of a separate sleeve carrying 
iase or zero line instead of having this line on 
iarrel which is rigidly attached to the spindle. 
Starrett Company's instructions for using this 
od of adjustment are as follows 
ke up the wear of the screw and nut, then 
ve all dirt from the faces of the anvil and 
le and bring them carefully together. Insert 
mall spanner wrench in the small hole and turn 

the line on the sleeve coincides with the zero 
>n the thimble. 



94 WORKSHOP GAUGES 

Heavy Micrometer Calipers. 

FOB, special usages and for large scale work, 
numerous forms of heavy micrometer calipers have 
been introduced. Standard forms of these instru- 
ments, to read either in Bntish or in metric measure- 
ment can be obtained, having ranges of from 1 to 
2 in. up to from 11 to 12 in., and from 25 to 50 mm. 




Brown & Sharps Mfg Co 

Fro 50. MICBOMETER CALIPEB FOB, MHASUBINO 
PISTONS. 

up to from 275 to 300 mm. The spindles and the 
screwed portions are of larger area than in the case 
of the ordinary form of micrometer calipers. 

The micrometer caliper shown in Fig. 50 is 
designed specially for measuring pistons in motor 
service work. Its range of measurement from 2 to 
6 in., by thousandths of an inch, covers all pistons 
ordinarily used. 

This range of measurement is obtained by the 
four anvils furnished with the micrometer. These 
anvils are easily and quickly changed, and held 
positively in place by a knurled nut. One anvil is 



MICROMETERS 



95 



measurements from 2 to 3 in., another from 
;O 4 in., and so on. 

In the Slocomb micrometer caliper (Fig. 61) the 
idmg line on the barrel is divided into forty parts 
r inch, corresponding to the pitch of the screw. 
L one side of the line these are grouped in fours 
mbered from 1 to 10 in the usual way (tenths of 




FIG 51 THE SLOCOMB MICROMETER CALIPER. 

inch), and on the other side of the line they are 
mped in fives, thus indicating eights of an inch, 
icimal equivalents are stamped on the thimble, 
e tool can be set by eights without any calcula- 
n or it can be used just as readily by decimals in 
5 ordinary way. The frames are of drop-forged 
.el of the section shown, and the range of the 
iper is 1 inch, the maximum size being from 1 to 
inches as required. 

ecial Forms of Micrometer Calipers. 

For the measurement of the pitch diameter of 
ew threads (i.e. the overall diameter of the screw 



96 



WORKSHOP GAUGES 



minus the depth of one thread), micrometers an 
supplied in which the spindle is pointed anc 
the anvil has the sam< 
form as the thread to b< 
measured. 

Where space is confined 
the frame of the micrometei 
may be cut away behind th( 
anvil so that the width ovei 
the latter is a minimum (sa} 
in.) ; or the whole frame 
may be given a rectangulai 
form, as in Fig. 52, so that th( 
tool can be passed through 
say, the bore of a milling 
cutter to measure the hut 
length, or through a boll 
hole to measure the thick 
ness of the adjacent plate 
On the other hand, i1 
may be desirable to use a 
micrometer the frame oA 
which has a specially deej 
throat so that a measure 
ment can be taken well awaj 
from the edge of a plate 
For the measurement of tube 
thicknesses, a rounded anvi] 
should be used ; this touches 
the inside of the tube at only one point, whereas a flat 
anvil would lie on a chord of the circle, thus causing 
the reading of the micrometer to be greater than the 




MICROMETERS 97 

ckness of the tube. In measuring the thickness 
paper, rubber, or other soft material, discs about 
a. diameter may advantageously be fitted to 
5 spindle and anvil, so that a reliable reading can 
taken without compressing the material measured. 
Che micrometer caliper shown in Fig. 53 is 
jcially convenient for measuring sheet metal. 




Brown & Sliarpe Mfg Co 
FlQ. 63. MlCHOMHTEB FOB MEASURING SHBET METAL 

placing the middle finger of the right hand 
ough the ring, the caliper is held at right angles 
the sheet to be measured and readings made while 
this position. The thimble is operated by the 
efinger and thumb of the same hand. To facili- 
e the readings of the caliper while held in position, 
; one-half thousandth readings are taken from the 
1 at the top of the spindle, the readings bemg 
icated by the pointer, and the twenty-five 
>usandths readings, or those corresponding to 
; readings on the barrel of an ordinary micrometer 



98 WORKSHOP GAUGES 

caliper, are taken from the scale at the top c 
frame. 

The decimal equivalents stamped on the 




Brown <t Sharps M 
FlG 54 MlOBOMETER DEPTH GAUGE. 

are convenient and render possible the imm 
expression of readings in 8ths, 16ths, 32nd 
64ths of an inch. When calibrated in E 




Brown A Sharps Mfg 

FIG. 55. SQUIBING MIOBOMBTEB FOR SETTING OT 
DEPTH OT GEAR TBHTH, ETC 

measure the tool measures all sizes up to 1 
half -thousandths of an inch (0-0005 in.) and q 



MIOBOMETEKS 99 

usandths are easily estimated. The caliper is 
3 made to measure up to 13 mm. by hundredths 
i millimetre. 

["he use of depth gauges has already been ex- 
ined (p. 77), and a micrometer gauge of this 
>e is at once convenient and accurate. The 
irometer screw in the gauge shown in Fig. 54 
3 a movement of 1 in. and the range of to 3 in. 
Dbtained by the use of the three measuring rods 
nished. The desired rod is easily and simply 
erted in the gauge through a hole in the 
crometer screw. 

The scribing micrometer illustrated in Fig. 55 is 
signed for scribing a line on gear blanks to indi- 
je the extreme depth to which the teeth are to 
cut. In this service it is specially economical 
that it avoids the necessity for keeping a large 
mber of separate gauges for different pitches. 
ie tool is also handy as a scratch gauge for scribing 
es and measuring spacing within its range, viz., 
i to 1 in. by thousandths, or up to 25 mm. by 
mdredths. A clamp screw is provided for clamp- 
g the spindle and preserving the setting. 
Micrometer heads, such as that illustrated in 
g. 56, can be attached easily to tools or machines 
h.en fine measurements are required, and the inside 
icrometer caliper set, shown in Fig. 57, is designed 
r internal and linear measurements, e.g. measuring 
flinders and rings, setting calipers, comparing 
luges, measuring parallel surfaces, and so forth, 
lie micrometer screw in the head has in. or 1 in. 
ovement, as required, and, by means of the 



L S Starrett Co 

FIQ. 56 MICROMETER CALIBER HEAD BEADING TO 
THOUSANDTHS OF AN INCH. 




L S Starrett Co , Ltd 
FIQ 67 INSIDE MICHOMETEB CALTPER SET. 



MICROMETERS 101 

nsion rods, measurements can be made from 
. up to 32 in. 

any other applications of the micrometer 
3unng screw might be mentioned, but enough 
been said to demonstrate the utility of this 
ce and the general manner of its use. 




CHAPTER V 

MARKING OFF 

Surface Plates. 

THE " surface plate " is a metal plate having a 
true flat surface and is used as a test plate for other 
surfaces. It is used extensively in the various 
operations of marking out, laying out, and testing 
work, and, in particular, in the various operations 
incidental to the preparation of work for machining. 
Surface plates are made of oast iron, or, alternatively, 
of hardened cast steel. Ordinary oast iron surface 
plates are surfaced with files and scrapers ; chilled 
cast iron and hardened cast steel surface plates 
have their surfaces ground, since they cannot be 
satisfactorily cut with steel tools. Until compara- 
tively recent years a chilled or hardened surface 
plate could not be surfaced so truly as one finished 
by filing and hand scraping, but the great improve- 
ments in grinding machinery of recent years* have 
enabled the hardened surface plate to be now 
produced to a high degree of accuracy. 

The production and use of a true plane surface 
is inseparably associated with accurate machine 
shop work and precision measurements. This 
fact is easily appreciated, but it is not always 
realized that anyone possessed of patience and a 
reasonable degree of manual skill can " originate " 

* See also Grvndvng Machines and their Use, by T. R Shaw. 
(Pitman's Technical Pnmer Series, 2s. 6d. net.) 

102 



MABKING- OFF 103 

ice plates by Whit-worth's method. If one 
ice plate be available another can be made to 
., but Whitworth's method enables one to start 
i three rough castings and to derive therefrom 
e surface plates accurate to the highest degree 
mable by a skilled craftsman. The procedure 
'oadly as follows: One pair of plates is planed, 
hipped and filed, until the surface of each is, 




Fia. 58. THE FACT THAT Two PLATES FIT is NO 
GUARANTEE THAT THEY ABE PLANE 



narily speaking, " flat." The surfaces are then 
jed together, using red lead to mark the high 
.s, and the latter are removed by means of a 
per until finally the pair of plates bed perfectly 
on the other. Though these plates bed perfectly 
e is no guarantee that they are truly plane, for 

might be concave and the other convex to 
stly the same curvature, as shown exaggerated 
'ig. 58. The third plate is now worked up until 
>eds perfectly on plate No. 1. Finally, the 

3 plate is tried with the No. 2 plate if it fits 
ectly, then all three plates are truly plane ; 
rersely, if all three plates be not truly plane, 
i it is impossible for No. 1 to fit No. 2, No. 2 
t No. 3, and No. 1 to fit No. 3. The reason for 

-(i383) 



104 WORKSHOP GAUGES 

this is evident from Fig. 59 ; Nos. 1 and 3, both 
being convex, fit the concave No. 2 plate, but NOB. 
1 and 3 will not fit each other. 

In practice it would obviously be wasteful of 
time and labour to bed two of the plates perfectly 
only to find from the third surface, that they were 
not plane. The actual procedure adopted is one 
which brings all three plates progressively nearer 




FIG 59 THBBE PLANES WHICH ABJE NOT PLANE 
CANNOT FIT IN ALL COMBINATIONS 



to a true plane. W. H. Pretty's cycle of operations, 
as quoted in Mechanical Engineering* is as 
follows 

The plates are stamped with numbers (1), (2), 
(3), in conspicuous places, and the planing tool 
marks are eliminated with a smooth file. Then 

(1) Using (1) as a standard: bed (2) to (1) ; 
(3) to (1) ; and (2) to (3), working equally on each. 

(2) Using (2) as a standard: bed (1) to (2) ; 
(3) is already bedded to (2) ; then bed (3) to (1), 
working equally on each. 

(3) Using (3) as a standard: bed (2) to (3) ; (1) 
is already bedded to (3) ; then bed (1) to (2), working 
equally on each. 

(4) Using (1) as a standard: bed (3) to (1) ; (2) 

* By W. J. Lmeham (Ohapmaai & Ha 1 !) 



MARKING OFF 105 

eady bedded to (1) ; then bed (2) to (3), working 

Uy on each. 

us cycle of operations is repeated until sufficient 

racy is obtained. 

raight edges may be originated in similar 

aer, and when these are being worked up they 

Id be reversed end for end occasionally, so as 

iminate all possible errors. 




Brown & Sharpe Mfu Co 
FIG 60 STANDARD CAST IBON SURFACE PLATES. 

st iron surface plates are generally procurable 
ses ranging from 4 in. by 3 in. up to 36 in. by 
; these plates can be obtained guaranteed 
-ate to I/ 1000th in., but are actually finished to 
nsiderably finer degree of accuracy. In the 
Lanically finished surface plates two grades 
ish are normally available, the first grade being 
mteed accurate to 1 /5000th in. and the second 
3 to l/1000th m. The latter are suitable for 
iary workshop use and the former are generally 
oyed for special purposes. The cost of Grade 
btes is usually about 50 per cent more than that 
ade B plates, 
pical surface plates are shown in Pig. 60. 



106 WORKSHOP GAUGES 

The shape of a surface plate is of very great import- 
ance, since any sheet or bar of metal tends tc 
deflect from its normal outline consequent on its 
own weight or the weight of any body placed upor 
it. Also, in the case of a casting, if the form of th 
plate be not chosen carefully there may be interna 
contraction stresses in the metal which will resull 
in warping, particularly under conditions t)f variable 
temperature. 

To overcome these difficulties the body of 
surface plate is heavily ribbed, the nbs being ar 
ranged to be of equal lengths and equal in thickness 
to that of the plate itself Under variations o 
temperature the ribs will not then expand or con 
tract more than the body of the plate, and th< 
warping which would accompany unequal expansioi 
is avoided. 

Ordinary surface plates are generally providec 
with handles for lifting (see Fig. 60) ; wood coven 
for the protection of the surface of the plate fron 
accidental injury are also obtainable as a standarc 
article. 

Angle surface plates are procurable in a variety o 
forms and dimensions and are used in conjunctioi 
with a flat surface plate. Angle plates of thi 
type are used in a considerable variety of way 
where it is necessary to true a surface standing a 
an angle to another surface. 

Scribers and Scribing Blocks. 

The scnber is a steel tool with a hardened point o 
edge which is used to mark centre lines, profiles, etc 



MARKING OFF 107 

L etal or wooden parts as a guide to subsequent 
lining or other operations, 
e ordinary form of hand scriber is a very simple 
1 consisting simply of a. length of steel rod with 
ijp and hardened point. Mechanics frequently 
r to make up their own scribers and innumer- 
forms are to be seen in regular daily use, the 
n, in most cases, being according to the fancy 
ingenuity of the individual user. For those 
prefer a more elaborate article, many special 
g of scribers are obtainable. Most of these 
>rovided with a special knurled stock, to give 
n hand grip on the tool. Others are furnished 

points at each end of the stock, one being 
i.e ordinary straight form and the other being 

at right angles to the axis of the tool. The 
r type of point is very useful for certain classes 
Drk, as, for instance, in reaching through holes 
other inaccessible positions. Pocket scribers 
hich the scribing tool is carried in a body 
on of the instrument when not in use are also 
inable in various forms. 

is often necessary, when laying out work, to 
e lines at a predetermined height from some 

of the work, or to continue lines over the 
us faces or surfaces In effecting this a surface 
e is generally used, this being essentially an 
ument with a heavy base carrying a pillar 
hich a scriber is attached by a clamp which 
its it to be adjusted vertically and horizontally, 
simple form of surface gauge is shown in Fig. 
md a more elaborate gauge of this type in 



108 



WORKSHOP GAUGES 



Fig. 62. In the instrument shown in Fig. 61 the 
spindle has a vertical movement and the base is 
cut out so as to permit of the instrument being used 

as a depth gauge. For 
fine adjustment the spindle 
in the base is raised or 
lowered by a knurled nut 
and all backlash is taken 
up by a spiral spring in the 
base. An extension can be 
coupled to the spindle for 
lengths greater than 12 
in. 

Several varieties of this 
type of gauge are avail- 
able in which the spindle 
is provided with a rock- 
ing bracket at its base so 
that it may be set either 
upright or at any desired 
angle, or it may be 
turned so as to permit of 
the scriber being used at 
a level below that of the 
base of the instrument. 
For example, in the instru- 
ment illustrated by Fig. 
62, a wide range of adjust- 
ments can be readily made 
by means of the knurled adjusting screw. The 
spindle and the bolt and bushing through which it 
passes are locked in the position of approximate 




L S Starrett Co , Ud 
FIG 61 SUIWAOE GAUGE 
WITH SPINDLE HAVING VER- 
TICAL MOTION ONLY 



MASKING OFF 109 

istment by the knurled nut at the boss on the 
). The fine adjustment can then be used to 
lin the exact setting. 




Brown & Sharpe Mfg Co 
Fid. 62 UNIVERSAL SUBFAOE GAUGE. 

'he base has Vee-groves in the bottom, so that 
tool can be used against circular work as well 
lat surfaces The two gauge pms in the rear end 
he base can be pushed down and used against the 
e of a plate or the side of a T slot. The spindle 
vels, can be securely clamped in any position 
GO. the vertical to the horizontal, and the scriber 
y be used below the base as a depth gauge. For 



110 WORKSHOP GAUGES 

small work the spindle may be removed and the 
scriber inserted in a hole in the spindle swivelling 
bolt, where it is readily adjusted. This type of 
instrument is obtainable in sizes ranging from 4 in. 
to 18 in. lengths of spindles, and is in every way a 
valuable aid to accurate workmanship. 

Straight Edges. 

Straight edges are employed for testing the 
straightness of a surface m one direction only, and 




FIG. 63. STEEL TBY S QUAKE. 

for scribing straight lines. They are obtainable with 
a plain rectangular section and also with one bevelled 
edge. In other forms, straight edges are graduated 
along one or both edges on one side with British 
standard or with metric scales They are usually 
procurable from 12 up to 72 in. in length, 1 in. up 
to 3 in. wide, and from -fa up to f in. in thickness. 
In metric measurement they can usually be obtained 
in sizes corresponding approximately to the above 
measurements. 

Set or Try Squares. 

The set, or try square, in its simplest form, 
consists of a rectangular back B (Fig. 63) holding a 



MAJRKLNG OFF 111 

3, the edges of the back and of the blade being 
right angle to one another and truly straight, 
enerally used by a mechanic, the set square is 
nge to test whether one face of a piece of work 
is truly at a right angle to another face. In 
the block B is bedded truly against the work, 
the blade is brought to touch at some part 
ist the face to be tested. 

the majority of set squares the blade is finished 
L ; in some cases, however, the blade is engraved 
a scale graduated either to British or to metric 
iurement. Set squares are generally obtainable 
zes varying from 1 m. length of block and 1 in. 
jh of blade, up to 12 in. length of block and 
. length of blade. 

bination Squares. 

my special forms of squares are now available 
pecial and general purposes. Typical examples 
ie most generally useful of these appliances are 
n in Eigs. 64 and 65. These instruments can 
sed for all purposes where an ordinary try or 
quare is used, but differ from the usual form 
pare in that the head can be caused to slide 
y the blade and can be clamped at any desired 
.ion. A spirit level and a mitre block are com- 
i with the square and a scnber is held f nationally 
e head in a small brass bushing. The set shown 
ig. 65 includes a protractor head with a level 
:he back) at right angles to the one on the 
re. 



112 



WORKSHOP GAUGES 



The combination square can be used as a simj 
rule, square, mitre, depth gauge, height gauge ai 




L. S Starrett Co , Ltd. 
FIG 64. COMBINATION- SQUARE. 

level ; and, with the auxiliary centre head, it fon 
a centring square for both inside and outside wor 




Brown & Sharps SIfg Co 

FIG. 65. COMBINATION SET ; ENGLISH, METRIC, 
OB ENGLISH AND METRIC. 

In its ordinary form it is procurable in sizes of fro 
4 to 24 in. length of blade. 



Protractors. 



oases the 



or can be read 
66 shows the 
on 



** all 



on the reverse 
bevel 



1 70 



axe used. 
factor consists of a 




I n 
* i 
can 



proteactor 
in Engllsh; 

, , ! a 8 P iri t level 
f the 



6? 



114 WORKSHOP GAUGES 

Fig. 68 very small angles can be established q 
and easily. In both of the appliances illustral 
Figs. 67 and 68 one side of the tool is flat 
allowing it to be laid flat on the work. The 
graduated in degrees for the entire circle, i 
vernier reading to 5 minutes (6' or -fa of 1) g 
increases the accuracy of measurement. Fii 
justment is provided by means of a small 1 




Brown & Sharps Mfg 

FIG. 67 UNIVERSAL BEVEL PROTRAOTOR WITH 
VERNIER. 

screw which is furnished as an attachment, 
blade can be moved to and fro, throughc 
length, and clamped independently of the dial 
The principle of the angular vernier is id 
with that of the linear vernier already des 
(p. 38), and the manner of reading it will be o 
from Fig. 69. Each space upon the vernie 
minutes shorter than two spaces on the true 
When the line marked on the vernier co 
with the line marked on the true scale, the 
of the base and blade are parallel. When the 
head is moved so that the line on the vernier r 



MASKING OFF 



115 



joincides with the line next hut one to on the 
e scale, the included angle of the base and blade 
i been changed one-twelfth of a degree, or 5 

autes 

Co read the protractor setting, read off directly 

m the true scale the number of whole degrees 




Brown <b Sharpe Mfg Co 

FIG 68 UNIVERSAL BEVEL PBOTRAOTOB WITH 
VEBNIER AND ACUTE ANGLE ATTACHMENT 

>tween and the of the vernier scale. Then 
,unt, in the same direction, the number of spaces 
Dm the of the vernier scale to a line that coin- 
des with a line on the true scale ; multiplying this 
imber by 5, the product will be the number of 
inutes to be added to the whole number of degrees. 

EXAMPLE As the vernier IB shown in Fig 69 it has moved 
; whole degrees to the right of the upon the true scale, and 
ie eighth line on the vernier coincides with a line upon the 




116 



WORKSHOP GAUGES 



true scale as indicated by *. Multiplying 8 by 5, the product, 4 
is the number of minutes to be added to the whole number 
degrees, thus indicating a setting of 12 degrees and 40 mmut 
(12 40'). 




FJO 69 ILLUSTRATING METHOD or READING AN 
ANGULAR VERNIER. 

The draughtsman's protractor shown in Fig. 1 
is a simple but useful instrument which can be s< 




Brown A Sharps Mfg Co 

FIG. 70 DRAUGHTSMAN'S PROTRACTOR WITH 
VERNIER READING TO 6 MINUTES. 

quickly to any angle, and used either side up and c 
either of the -two outside edges of the frame. ! 
can be used to advantage in dividing a circle, tran 
ferring angles or laying off a given angle, withoi 
resetting, on either side of a line. In the drawir 



MARKING OFF 



117 



ce this protractor forms a convenient extension 
a T-square and frequently takes the place of 
and 60 set squares. 

1 Test Gauge. 

?he dial teat indicator (Pig. 71) is of great assist- 
e in determining the accuracy or otherwise of a 




Brown ds Sharpe Mfg Co 

FIG. 71 DIAL TEST GAUGE POB USE ON Strap AGE 
PLATES AND THE LIKE 

surface or of the movements of a spindle, arbor, 
. The movement of the measuring surface that 
us upon the work is magnified a number of times 
1 indicated by the pointer on a dial, which reads 
thousandths of an inch (or hundredths of a milli- 
tre), and is adjustable to allow the zero to be set 
any required position. The spindle has Jin. (or 
im.) movement. 



118 WORKSHOP GAUGES 

The arm carrying the indicator can be removed 
from the post and used independently, as in the 
tool post of a lathe, and the measuring point is 
removable to allow the use of different forms. As 
shown in Pig. 71 the indicator is used in conjunction 
with an attachment which consists of a bracket 
carrying a pivoted lever, one end bearing on the 
measuring point of the indicator and the other on 
the surface investigated. This attachment enables 
the dial indicator to be used in testing internal and 
other surfaces which cannot conveniently be reached 
by the straight spindle of the indicator itself. 




CHAPTER 

SELECTION AND OABE OF INSTRUMENTS 

of the first importance that a mechanic desirous 
lalifying himself for efficiency in high class work 
Id possess a set of instruments which will 
>le him to take measurements of all kinds with 
jh degree of precision. The accuracy of rueasure- 
t to be realized will vary to some extent with 
nature of the work upon which he is engaged, 
instruments of precision are a prime necessity 
pery case and to every mechanic. 
i all cases it should be remembered that a 
Avely few, carefully selected and well kept 
uments or tools, of the best workmanship 

design, will be of far greater practical value 
L a larger assortment of miscellaneous " gadgets " 
oubtful accuracy and indifferently kept. Well- 
fa, accurate instruments are generally expensive 
le first place, and they are only of practical value 
)ng as they are properly looked after. 

ctioru 

L no case should a heterogeneous collection of 
:ellaneous instruments be purchased ; each tool 
dd be selected individually after the complete 
;e of work to which it is to be applied has been 
fully considered. Advice from experienced 
sers is helpful and should always be listened to, 
it is generally a mistake to follow others' advice 

-(5383) 119 



120 WORKSHOP GAUGES 

too slavishly. In the use of workshop tools am 
measuring appliances the personal factor enter 
largely into consideration. The correct attitud 
for the young mechanic in this connection is to lean 
all that there is to know regarding the experience 
of others, and to apply this to his own persona 
peculiarities and needs He should, in fact, cultivat 
the habit of considering all the conditions of wor] 
for himself with a view to coming to a definit 
decision as to what will meet his own persona 
requirements. 

The procedure in general should follow broadl 
the following lines. 

(1) The conditions for which the instrument i 
required and all the purposes to which it will b 
applied should be passed in review and noted dow 
in writing. 

(2) The best type of tool, i.e. the design be* 
suited to the full range of requirements should the 
be decided upon. 

(3) The fullest information from all sources shoul 
be obtained, and the various makes of this particul* 
instrument should be investigated thorough!; 
Manufacturers' lists are very helpful in this conne 
tion, but should not be taken as the only guide 
they should be supplemented by a certain amoui 
of advice from more experienced workers and all 
by the would-be purchaser's own mechanical knot 
ledge, as well as by a study of his own person 
experience. 

(4) The instrument should be selected fro 
stock if possible, but in any case the deal should n 



SELECTION AND CARE OF INSTRUMENTS 121 

nally closed until the intending purchaser has 
Jed the goods, and satisfied himself tha,t it 
.s his own personal requirements as regards 
it of work to be covered and hmits of accuracy 
3 attained. 

many cases the deciding factors as regards 
rent makes of similar tools are (1) soundness of 
;n , (2) quality of material , (3) fineness of 
manship , (4) range of measurements. As 
*ds wearing or lasting qualities, apart from 
ars' guarantees, it is necessary to rely to a 
iderable extent on the experience of others, 
in this connection it is important to remember 
ultimate accuracy of workmanship is contingent 
tiese points. 

many oases, workshop instruments are pur- 
ed from fellow workers, but it is false economy 
ly instruments in this way simply because they 
heap In all such cases the intending purchaser 
} ask himself firstly, does the instrument fulfil 
,ctual requirements, and, secondly, is it capable 
ving consistently accurate results 1 Inaccurate 
, are a constant source of disappointment and 
in no case give good results as regards finished 

1. 

is not possible within the space of the present 
: to give any tabulated list of the tools or 
uments which a mechanic should possess, 
5 such lists would have endless variation accord- 
bo the precise nature of the work upon which 
mechanic is engaged. He should in all cases 
pile his own lists, and should do so only after 



122 WORKSHOP GAUGES 

very careful consideration on the lines rougl 
laid down above. The assembly of a good tool 
should be a gradual process of building up, and 1 
guiding principle should be that the best is inevital 
the cheapest. 

Care of Tools. 

Nothing indicates slovenliness and inefficier 
in a workman more readily than the presence 
his tool kit of dirty, rusty, and damaged to< 
This is true of tools as used for general purpos 
and doubly so when applied to workshop gau 
and measuring appliances, since the sole justificat 
for the existence of such instruments is their cl 
approximation to absolute accuracy. If an ordini 
tool is not in perfect condition it may still be mi 
to serve some useful purpose in skilful hands, 1 
the damaged or inaccurate gauge or measur 
appliance must either be put aside immediately 
damage or inaccuracy is discovered and must 
duly repaired, or the instrument must be scrap] 
and broken up immediately. The presence 
defective instruments in a mechanic's kit m 
and frequently does, lead to costly mistakes 
workmanship as a result of their use. 

Workshop gauges and measuring appliances ir 
therefore be looked after most carefully. T 
must never be left lying about or kept loosely 
haphazard amongst other tools. When not actu 
in use they should be kept packed away in s< 
special and properly designed receptacle, should 
taken out and handled only when actually nee 



SELECTION AND CARE OP INSTRUMENTS 123 

Jhe work in hand, and should be used with the 
/test possible care and discrimination, all forcing 
rough handling being scrupulously avoided. 
y should always be wiped over with a clean 

oily rag immediately after use, and should be 
raed to their case or permanent resting place, 

never left lying about on the working bench. 

odic Tests for Accuracy. 

he frequency of tests for accuracy will largely 
and on the extent to which instruments are in 
In all cases they should be gauged for accuracy 
ntervals of, say, every four weeks, and should 
Edition be tested immediately before engaging 
my work of special importance where the highest 
aible degree of accuracy is essential. It is not 
sssary to lay down rules for the testing of each 
vidual type of workshop instrument, but certain 
ninent causes of possible inaccuracy may be 
itioned briefly. 

es. 

part from extreme variations of temperature, 
1 rules are not liable to become inaccurate in 

except as regards " end " wear, that is, the 
lual wearing away of the two ends of the rule 
a result of prolonged use. With the modern 
B of hardened steel rule, end wear is a very 
lual process, but nevertheless the accuracy of 

end divisions should always be held under 
jicion and should be checked from time to time 



124 WORKSHOP GAUGES 

by testing against a rule which is known to I 
accurate. The possibility of error from this cam 
is, however, always present, and whenever prai 
tica~ble measurement should be taken not from or 
or other of the extreme ends of a rule, but from son 
intermediate division, e g from the 1 in. or tl 
1 cm. division mark. 

Ivory and boxwood scales . or rules undergo 
gradual shrinkage process with time, and are n< 
to be relied upon for work where extreme accurac 
is required unless they are practically new or unle 
their accuracy is checked at frequent intervals 

Steel Tapes. 

Steel tapes are sometimes found to stretch a 
preciably, and for regular use in a workshop th> 
must be checked for accuracy at frequent mtervt 
against a fixed standard dimension, such tee 
should be earned out at, or as near as practicab 
the same temperature each time that the steel ta 
is checked, to avoid any possible overestimate 
the inaccuracy, or, alternatively, any cancellati 
of the error, consequent on appreciable temperati 
differences. Steel tapes which have been brok 
in use should never be repaired except by t 
actual makers, who, generally, have special methc 
and facilities for carrying out such repairs withe 
impairing the accuracy of measurement. In gener 
steel tapes when new are guaranteed by the mak 
to be accurate at a given tension, say 10 poun 
when supported over their entire length 



SELECTION AND CARE OF INSTRUMENTS 125 

pers. 

he measuring edges of the jaws of slide calipers 
old be minutely examined from time to time to 
jrtam whether (1) the fixed and adjustable 
es are truly parallel, the one to the other through - 

their extent, and (2) the edges are truly straight 
Dughout their extent Rough usage on pieces 
Fork may in time produce wear on the measuring 
es, and the instrument is then useless for accurate 
k and should be sent to the makers for repair. 
?he locking screws of slide calipers and the contact 
faces between the adjustable edge and the body 
the instrument should be examined from time 
time. Too heavy a hand in locking the adjust- 
e edge on the body of the instrument will cause 
sessive wear on the contact surfaces, and this, 
turn, will tend to give inaccuracy of results, 
e sliding contact between the adjustable portion. 
1 the body of the instrument should be such that 
ire is definite friction between the moving parts 
b not sufficient friction to cause undue wear on the 
>bing surfaces. 

The ordinary patterns of inside and outside 
ipers are now generally made with the joint 
med with a screw threaded into a nut or stud, 
nsion on the point can thus be varied at will, 
d a uniform degree of friction of any desired 
lount can be obtained to suit the individual needs 
the user. The surface of the points should be 
amined at frequent intervals to avoid using the 
jtrument when there are burrs or indentations 

the measuring points. Needless to say, such 



126 WOBZSHOP GAUGES 

scoring of the measuring points should never occur 
with proper usage, but neglect and rough handling 
may be, and unfortunately frequently is, their lot, 
hence the precaution of frequent examination is 
a wise one. 

Combined inside and outside calipers are intended 
to give the same measurement at the points of both 
the inside and outside calipers; they can be relied 
upon in general to do this when new, but as they are 
generally used to a greater extent as either inside 
or outside calipers, frequent examination and 
checking is necessary to ensure that one set of 
points is not becoming more worn than the second 
pair of points. Their accuracy in giving identical 
measurement at both sets of points should always 
be under suspicion, and examination and checking 
of their accuracy must be earned out at regular 
intervals. 

The special fittings of some calipers, such as 
screw thread adjustment (see p 53) need particular 
attention from time to time. The accuracy of fit 
between the fine adjustment screw and its nut, 
and the absence of wear between these parts, 
is an important feature as regards the accuracy and 
reliability of instruments of this class. 

Micrometer Calipers. 

Micrometer calipers in their various forms are 
particularly liable to damage from rough handling 
The fixed anvil and the end of the moving spindle 
are the points between which measurement is made, 
and a certain amount of wear on these surfaces is 



SELECTION AND OABE OF INSTRUMENTS 127 

ritable with time and use. In some makes of 
/ruments of this class the anvil is made to be 
ustable in relation to the frame of the instrument 
jompensate for wear on the measuring surfaces ; 
[ in other makes the base or zero line is earned 
a, friction sleeve placed over the barrel in relation 
which it is adjustable. With the latter type of 
irument adjustment for wear is obtained as 
uired by rotating the friction sleeve on the 
rel until the line on the sleeve coincides with the 
D line on the thimble. 

nstruments which fail to give consistently 
orate results on repeated tests of a known dimen- 
i should be scrapped ruthlessly , they are of no 
to the mechanic and are a hopeless impediment 
accurate workmanship. 

'e Gauges. 

Vire gauges of reputable make are supplied in 

cially hardened steel The width of the notches 

equal to recognized standards of measurement 

pp. 62 et seq ). Measurement of gauges inter- 

3iate between any two accepted standards cannot 

ietermined accurately by this means, and in such 

as it is necessary to determine into which notch 

work will pass and at which notch it will just 

pass. It follows that, in time, friction of the 

cles being measured tends to cause minute 

irgement of some of the notches, so that the 

uracy of the gauge as regards a portion or the 

Die of its range is lost Wire gauges should 

refore be frequently and periodically checked, 



128 WORKSHOP GAUGES 

and they should be instantly rejected for work 
when wear on any of the notches becomes evidenced. 
Instruments of this class cannot of course be ad- 
justed and their replacement by new and accurate 
gauges at intervals is essential to good workmanship. 

General. 

The centring points of all such instruments as 
scribing calipers, and the points of scribing styles 
require attention from time to time. The points 
must of necessity be kept sharp and the metal of 
the points must be specially hardened Blunt 
points mean indefinite marking, and, therefore, 
inaccuracy on the work 

With hinged and jointed instruments of all 
classes it is of great importance to see that the 
joint has the requisite degree of friction for the 
work involved. Too little friction may result in 
errors of measurement by slipping ; too much 
friction involves possibilities of straining the instru- 
ment during setting, difficulty (and consequently 
error) in getting the precise adjustment, and excessive 
wear at the joints. 

The greatest care must at all times be exercised 
in preventing accidental damage to the worlung 
edges of instruments of the straight edge, try square, 
and level protractor types. Such instruments must 
on no account be left on the working bench when 
not m use, neither should they be placed loosely 
with other tools in a box or drawer, but they should 
always be secured in a proper case or fitting where 
they are safe from accidental injury. 




CHAPTER 

LIMITS AND FITS 

meral Considerations on Classes of Fits. 

r iTH the exception of certain special cases, the 
lestion of " fits " and corresponding " clearances," 
id " limits " or " tolerances " concerns only cylin- 
-ical work. Theoretically, a shaft which " fits " 
hole should have a diameter exactly equal to the 
ameter of the hole but in machine shop work, 
j in most other branches of practical work, exacti- 
ide is only a relative term. The cost of finishing a 
irface increases rapidly as one imposes closer 
mits upon the accuracy of the dimensions of the 
Lece, and the limits to which one should work in 
ractice affect materially the cost and efficiency of 
reduction and are determined by the purpose to 
e served. A perfectly cylindrical shaft in a per- 
jctly cylindrical hole of the same diameter would 
e free to slide or rotate. The shaft would, however, 
3uch every part of the hole and there would be no 
3om for a film of lubricant. For this reason, and 
ecause perfectly cylindrical shafts and holes can 
e neither produced nor maintained in service, an 
xact fit is not even theoretically desirable where 
Liding or rotation of the shaft is required ; there 
lust be some clearance to allow for irregularities 
f the surfaces, to make lubrication possible, and to 
revent " binding " of the surfaces. On the other 
and, if the shaft be required to drive or hold the 
129 



130 WORKSHOP GAUGES 

part in which it is inserted, the diameter of the 
shaft must be larger than that of the hole so that, 
whether the shaft be forced into the hole or whether 
the collar, flywheel, etc , be shrunk on to the shaft, 
there will be internal stresses in the two parts 
preventing relative motion between them In the 
theoretical case of the shaft, which is an exact fit 
in the hole, the two parts touch, but there is no 
force between them, other than that due to their 
own weight,* and motion of the shaft cannot be 
transmitted to the collar. In the practical case 
approximating as closely as possible to this theo- 
retical case, there would be sufficient irregularity 
of surface and sufficient fnctional grip to enable 
the shaft to carry the collar with it against small 
resistance, but not against any appreciable or well- 
defined resistance. Popularly speaking, the " exact 
fit " in question would be neither one thing nor the 
other it would be too tight for running and toe 
loose for driving. 

From these general considerations it will be appre- 
ciated that a shaft and hole which are machined, aE 
accurately as commercially possible, to the same 
diameter will have to be forced or driven together 
The force required to mate them will be small, and 
we may say that they are a " light driving fit." H 

* If seizure occurs between the parts, as it may easily do li 
they are a very accurate fit, they become practically weldec 
together The extent of such seizure is, however, mdeter 
minate , the risk of its premature occurrence would make 
assembly practically impossible, and no reliance could be placet 
upon a seized contact for driving purposes. Except as a posaiblt 
danger where a clearance fit is really required, seizure is hew 
left out of consideration. 



LIMITS AiTD FITS 131 

e shaft be appreciably larger than the hole we 
i,ve a " heavy driving fit " or a " force fit," which 

" heavier," the greater the excess diameter of 
IG shaft. For a " sliding fit " or an " easy push 
. " the shaft must be definitely smaller than the 
>le. Tor a " running fit " the shaft must be yet 
nailer to provide for lubrication and to compensate 
r the binding action of deflection in the shaft, 
ccording to the clearance provided, we may have 

" close running fit " or a " slack running fit " or 
ren a " coarse clearance," and it is evident that a 
tuch larger clearance must be provided in the 
aarings of heavy machinery working in dirty 
tuations than in fine machines for precision work. 

units in Repetition Manufacture. 

So far we have considered only the class of fit 
etween a single shaft and hole, but the question of 
mits and tolerances reaches its greatest importance 
r here repetition manufacture is concerned. A single 
haft and hole can literally be " fitted " together to 
ny desired degree of closeness or slackness without 
sference to any outside consideration. On the other 
and, if it is desired that a nominal 1 in. shaft should 
t any one of thousands of 1 in. holes produced in 
Afferent shops and during a term of years with a 
learance suitable for a given purpose, then it is 
vidently of vital importance what interpretation 
i placed upon standard size, and what amounts 
,re allowed by way of tolerance for machining and 
learance for the service in question. 



132 WORKSHOP GAUGES 

Bases for Specifying Limits. 

The alternative bases on which it is possible t 
define limits and fits are : (1) The unilateral systen 
shaft basis ; (2) the unilateral system, hole basis 
(3) the bilateral system, shaft basis ; (4) th 
bilateral system, hole basis 

In the unilateral system, shaft basis, the diamett 
of the shaft is taken to be a constant factor, differer 
classes of fit being obtained by varying the actut 
diameter of the hole of the nominal size concernec 
The first British Standard Report on systems fc 
limit gauges (B.E.S A. Report No. 27 1906) recon 
mended that the shaft be the constant membe 
but this recommendation was not generally adopte 
by the engineering industry. The main practic* 
disadvantage of the " shaft basis " is that it involve 
a set of reamers for each nominal size of hol< 
differing from each other in diameter by the amounl 
of the limits for different classes of work. Th 
provision and maintenance of such reamers, differin 
only by some thousandths of an inch, are hot 
difficult and costly. On the other hand, whe 
working with a standard diameter of hole it : 
comparatively easy and inexpensive to turn shafi 
to the diameters required for various clashes of fits. 

"Tolerance" and "Allowance." 

These terms, which are often misunderstood an 
confused, are defined as follows in the origin* 
B.E.S.A. Report (No. 27) on Standard Limit Gauge 
for Running Fits 

Tolerance. A difference in dimensions prescnbe 



LIMITS AND FITS 133 

\. order to tolerate unavoidable imperfections of 
orkmanship 

Allowance. A difference in dimensions prescribed 
L order to allow of various qualities of fit. 



BRITISH STANDARD LIMITS AND FITS 

The new British standard report on limits and 
bs (B.E.S.A. Report No 1641924) recommends 
le adoption of the hole as the constant member, 
nd embodies a table of standard tolerances appro- 
riate to holes of different sizes and different grades 
E workmanship, so that all holes on the same system 
milateral or bilateral) of the same nominal size and 
le same specified grade, will be interchangeable. 

The principal difficulty in standardizing tolerances 
n holes lies in the fact that both the " unilateral " 
Astern and the " bilateral " system are used In 
le unilateral system the tolerance is in one direction 
tily from the nominal size and is generally positive, 
e. every hole is of nominal size or larger, and the 
ominal size is the low limit of the hole. In the 
ilateral system the tolerance extends in both 
ireotions not necessarily in equal amounts from 
le nominal size ; the latter lies between the high 
nd low limits of the hole, so that holes in the 
ilateral system may be either of nominal size or 
nailer or larger 

For the complete tables issued by the British 
Ingineenng Standards Association and a detailed 
xplanation of their use, the reader must of course 



134 WORKSHOP GAUGES 

refer to the report itself,* but the notes in tl 
following pages will serve as an introduction to tl 
subject. 

At present, bilateral limit gauges are used mo: 
extensively than unilateral limit gauges in th 
country, but an appreciable percentage of Britie 
users of the bilateral system have expressed the 
preference for the unilateral system, and tl 
tendency 'in standardization on the Continent ar 
in the United States is distinctly towards tl 
unilateral system. 

It is therefore recommended by the B.E.S j 
that the unilateral system be used in connectic 
with cylindrical mating surfaces in cases where 
does not conflict with predominating present pra 
tice. To allow for the fact that predomvnatii 
present practice will in some cases determine tl 
continued use of the bilateral system, the B.E.S... 
Report includes : (1) a table (abridged in Table X"^ 
herewith) giving two sets of hole tolerances, bast 
respectively on the unilateral and on the bilater 
systems ; (2) a table of graduated shafts suitab 
for pairing with either the unilateral or the bilater 
holes (see Table XVTI). These tables are giv< 
both in British (inch) and metric (miUimetre) uni 
so as to meet all requirements. All the table 
diagrams, and notes required for the use of eith 
of the systems, in either British or metric um1 

* Obtainable from the B.E.S.A., 28 Victoria Street, S.W 
Is. 2d. post free. Headers cannot be urged too strongly 
obtain this report and all the other B B.S.A. reports which be 
upon their work. In. addition to stating the British Standai 
for materials, machinery, apparatus, etc., these reports contf 
most instructive explanatory notes and other information. 



LIMITS AND FITS 135 

obtainable in the form of wall charts for drawing 
se or workshop use. 

ing and Non-mating Surfaces. 

efore proceeding further it should be explained 

j in deciding upon the system of gauging and 

amount of tolerances to be employed, one must 

mguish clearly between " mating surfaces," e.g. 

)le and shaft, in which the inter-relation between 

surfaces in contact is the guiding feature, and 

m-mating " surfaces in which only one surface 

to be considered. 

'he B.E S.A recommendation in favour of the 
ateral system is restricted definitely to mating 
'aces, because either unilateral or bilateral toler- 
es may be used for non-mating surfaces, the 
ice depending mainly on convenience in manu- 
iure. For example, if the article made tends to 
ome always bigger or always smaller, due to 
,r of dies, the tolerance might well be unilateral , 
jreas, if the dimensions are also dependent upon 
adjustment of the producing apparatus, such as 
3, a bilateral tolerance may be preferable. 

B.E.S.A. Standard Tables for Limits and Fits. 

.s already stated, these tables are here reproduced 

y in abbreviated form, but the particulars given 

enable the use of the tables to be understood 

the simplicity of the whole to be appreciated. 

'able XVI gives the unilateral and bilateral limits 

jolerance for holes. In the unilateral holes the 

limit of the hole is nominal size, i.e. there is no 

(5383) 20 pp 




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LIMITS AND FITS 137 

limit of tolerance and L = for all cases. In 

bilateral holes, the nominal size lies between 

high and low limits, which are positive and 

ative respectively. Provision is made for four 

idard grades of workmanship for holes, the B 

ilateral) and K (bilateral) holes representing the 

at accurate grade ; the U and X holes repre- 

ting those most commonly employed ; and the 

38, V, W, Y, and Z having larger tolerances. 

meet exceptional conditions, oversize holes A, 0, 

H are provided , these are common to both the 

Lateral and the bilateral systems, and have two 

itive limits of tolerance, i.e. the low limit of the 

3 is larger than the nominal size. Finally, yet 

er limits (/, Table XVI) are provided for the 

3S and shafts which are not required to mate. 

'able XVII gives the recommended limits of 

irance for a standard series of graduated shafts, 

.able for pairing, with either the unilateral or 

,teral holes. This table, which is common to 

unilateral and bilateral systems, provides for a 

es of 14 different fits with reference to any 

fcicular hole, by progressively changing the 

)osition of the tolerance m relation to the nominal 

. The actual value of the tolerance remains 

hanged for all shafts from F to M inclusive, 

se shafts being of the same grade of workman- 

) as a J5 hole (see Table XVI) The remaining 

Ets, Q to TT, are given increasing tolerances 

a,use they are all considerably undersize and 

'efore provide increasing amounts of clearance 

in assembled in any hole. 




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wtfirs 


SOUTH 





LIMITS AND FITS 139 

ibles XVI and XVII as here given cover only 
inal sizes from to 0-99 in. The corresponding 
BS in the B.E.S A. Report extend up to 25 in. 
mm ) and can be extended further by aid of 
jrs which are explained below. The nominal 
i are specified in ranges, the length of each 
,e being such that at each change of range the 
ance increase on U and X holes is 2 ten- 
isandths of an inch (0-0002 in.). 

Multipliers and Range Factors. 

ie size multipliers m and the range factors r, 
es XVI and XVII, enable the limit values in 

3 tables to be virtually " carried in the head." 
limit values are obtained by multiplying 

ther the appropriate values of m and r, odd 
ten-thousandths being omitted from the 
ucts in which they occur. 

AMPLE. For a nominal 0-5 in. U hole (Table XVI), 

4 and r = -f 0-2 and ; henoe the standard (unilateral) 
i are +0-8 and 0. For a Y hole of the same nominal 
<n = 4 and r = + 0-2 and - 0-2 ; henoe the standard 
era!) limits are + 0-8 and - 0-8. 

lough Tables XVI and XVII give all the vajues 
* they include only three values for m. The 
e of m for any other size of hole is calculated 
)llows 

D = nominal size of hole in inches, then m is such that 
m (m - 1) > 20 D = (m - 1) (m - 2). 

expression is solved very easily. 

A.MPISI. Suppose that the nominal diameter of the hole 
aft is 3f in., then 20D = 20 x 3J = 75, and we have to 



L40 WORKSHOP GAUGES 

bid two consecutive numbers, m and (m- 1), the product of 
vhich exceeds 75, whilst the product of the next lower consecutive 
lumbers (m - 1) and (m-2) is equal to or less than 75 In 
jther words, if we have three consecutive numbers, A, B, C, 
moh that 20D is intermediate between A x B and B x C, 
Jien m equals A, the largest of these three numbers. 

In this case 10 x 9 = 90, which is greater than 20Z>, and 
} X 8 = 72, which is less than 20D, hence m = 10. 

For a W hole, r = + 8 and 0, so that the limits (m x r) 
ire + 8 and , whilst for a K shaft, r = + 0-05 and - 0-05, 
aenoe the limits are + 0-5 and - 0-6. 

Standard Fits. 

The basis of the B.E.S.A. tables being a hole 
basis, the limiting dimensions of any hole of a 
particular quality and size remain unchanged, and 
varieties of fit are obtained by varying the actual 
dimensions of the shaft.* 

Table XVIII gives typical examples of the fits 
thus obtained between standard shafts (Table XVII) 
and U and X holes (Table XVI), these holes being 
chosen for the purpose of numerical examples, 
because the tolerances on them are those most 
commonly employed The limits of fit resulting 
from the assembly of the standard shafts in any 
of the other holes specified, are determined by taking 
the algebraic difference between: (a) the largest 
hole and smallest shaft , (6) the smallest hole and 
largest shaft. The results thus obtained are the 
upper and lower limits of the fit, and three cases 
must be distinguished 

1. If the smallest hole be greater than the largest 
shaft we have a clearance fit. 

2. If the largest hole be smaller than the smallest 

* The Association recognizes that exceptions to this rule are 
necessary in certain classes of work. 



N 







COCO 


** 


1010 




51 


W <O 


4100 


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rHO 
1 1 


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rHO 
1 1 


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ego 
1 1 


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mco 


ooo 


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iHO 
1 1 


(NO 
1 1 


MrH 
1 1 




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OrH 


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++ 


++ 


+ + 


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5OO1 
OrH 


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rHO 


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1 1 


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125 




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142 WORKSHOP GAUGES 

ihaft we have an interference fit, i.e obstruction, the 
imount of which is even greater with the smaller 
holes and larger shafts. 

3. The term transition fit covers cases inter- 
mediate between (1) and (2), i.e. cases in which the 
limits admit of either clearance or interference fits 
being obtained. 

EXAMPLES. (i) Suppose that an .27 shaft, nominally of Jin 
diameter, be used in a U hole , what are the limits of fit T 

From Tables XVI and XVII the largest hole is +0-8 thou- 
sandths of an inch oversize, and the smallest shaft is also 
+ 0-8 thousandths oversize , the allowance between these two 
LS therefore 0-8 - 0-8 = 0, i e an exact fit On the other hand, 
the limit for the smallest U hole is 0, and that for the largest E 
shaft is + 1-2 ; the difference is - 1-2 = - 1-2 thousandths, the 
shaft being the bigger The limits of fit in the case considered 
are thus - 1-2 to (see UE, Table XVIII), and the fit is always 
an "interference fit." 

(u) Proceeding similarly, it will be found that, for the same 
nominal size 

(a) A. D shaft in a U hole gives fits from - 0-8 to + 0-4, 
i.e. a " transition fit " 

(6) An M shaft in a U hole gives fits from + 0-4 to + 1-6, 
i e a " clearance fit " 

(c) An E shaft in an X (bilateral) hole gives fits from - 1-6 to 
- 0-4, i.e. an " interference fit " 

(d) A TT shaft in an X hole gives fits from + 4-4 to + 8-4, 
i.e. a " clearance fit," and a coarse one at that. 

The effect of transferring any standard shaft from 
a bilateral hole to a unilateral hole, is to increase 
the clearance or reduce the interference, i.e. to make 
the fit easier. An example of this may be seen by 
comparing Examples (i) and (li c) above. 

Specifying Fits. 

Even to-day it is not uncommon to find drawings 
dimensioned throughout with single dimensions. 
For example, a shaft and bearing may be marked 



LIMITS AND FITS 143 

in. diameter, but it is clear, from what has already 
;en said in this chapter, that the actual diameters 
ust differ by, say, 0-005 in to provide for a running 
i with suitable clearance for lubrication, etc. 
If the drawing bears only a single dimension it is 
ft to the discretion of the machinist or fitter to 
jcide what clearances should be provided and 
here. Obviously it is better, from every point of 
ew, to specify all the limits on the drawing itself. 
When the exact nature of a fit has to be named 
is recommended by the B.E.S.A. that the symbols 
' the hole and shaft be used in combination, e.g 
B, and marked on the assembly drawing in this 
rm The drawing of the hole and the drawing of 
le shaft can then be marked, in combination with 
le nominal size, say | in. U for the hole, and 
in. B for the shaft, meaning in this instance 
iat the hole is to be within the limits 0-5008 in 
rid 0-5000 m , and the shaft between the limits 
5004 in and 0-5000 in. (see Tables XVI and XVII). 
'his particular combination would include clearance 
ts and interference fits, i.e. it would be termed a 
'ansition fit. 

If preferred, the numerical values of the limits, 
istead of the corresponding symbols, may be 
pecified on drawings. 

Though such terms as " driving fit," " push fit," 
nd " running fit " have no well-defined meaning, 
hey are nevertheless very descriptive, and to many 
ersons they convey an idea of the quality of a fit 
lore vividly than would a numerical statement of 
he clearances. The actual value of the clearances 

10A (6383) 



144 



WORKSHOP GAUGES 



in a " running fit " is naturally greater for a large 
shaft than for a small one, but Table XIX shows 
values of the range factor r corresponding to various 
classes of fit as described in workshop terms. On 
multiplying the appropriate value of r by the value 
of m for the nominal size of hole and shaft concerned 
(this value of m being calculated as already 
explained), we obtain the numerical value of the 
limits for the nominal size and class of fit in 
question. 

TABLE XIX 

VALUES OP " RANGE FACTOR " r CORRESPONDING TO VARIOUS CLASSES OF 

PITH IN UNILATERAL D HOLES AND BILATERAL X HOLES 

NOTE Tho actual limits In thousandths of an Inch " m x r, where m Is the 

" size multiplier," calculated as explained on page 139 



Description of Fit 


Value of T 


Unilateral 


Bilateral 


Clearance Fits 


Coarse clearance 
E-rtra slack running 
Slack running 
Normal running 

Close running (2) 

Easy slide 
Slide or easy push 


+ 1 2to + 22 
+ S to + 1 4 
+ 5 to + 1 
+ 03to + 07 


+ 1 1 to + 2-1 
+ 07tO + 13 
+ 4 to + 9 
+ 2 to + 6 


+ 15 to + 5 
+ 01 to + 4 
+ 05 to + 35 
to + 3 


111 


Push 
Light keying 
Medium kpjdng 
Heavy keying 
Evtra light drive 


- 05 to + 25 
- 1 to + 2 
-0 IB to + 15 
-02 to + 1 
- 25 to + 05 


||| 


Light drive 
Heavy drive 
Force 


-OStoO 
-04 to- 01 
- 5 to - 2 



EXAMPLES (i) For a S^m. shaft, 20D = 70 and m = 9,* 
and from Table XIX r for a normal running fit = +0-3 to 
+ 0-7 for the unilateral system and + 0-2 to 0-6 for the bilateral 
system Hence the actual limits would be (TO X r) or + 2 7 
to + 6-3 thousandths of an inch for the unilateral U hole, and 
+ 1-8 to + 5 4 thousandths for the bilateral X hole. As already 

* 9 x 8 - 72 > 8 x 7, see page 139. 



LIMITS AND FITS 145 

bed, changing from the bilateral to the unilateral system 

ulta in an easier fit 

'11) What are the limits for a in (nominal) shaft which is 

[uired to be a push fit in a unilateral U hole ? 

Dn this case m = 5 and, from Table XIX, r = - 0-05 to + 0-26, 

ace the limits (m X r) are - 0-25 to + 1-25 thousandths of an 

>h or, say, - 2 to + 1-3 thousandths. These limits correspond 

the use of a K shaft m a U hole. 

oikshop and Inspection Gauges. 

Limit gauges are used to ensure that any given 
tnension is within the tolerance specified for the 
IBS of work to be produced. As already explained 
hapter III), in the case of cylindrical work, 
ese gauges may be either double male gauges, 
to end of which must enter, and the other end of 
iich must not enter, the hole to which it is applied ; 
they may be either two-ring or two-gap gauges, 
ie of which must pass over, and one of which 
ust not pass over, the plug or male piece to which 
ey are applied 

Workshop gauges are used in the course of manu- 
cture to ensure that no work falls outside the 
nits of fit specified by the standard tables adopted, 
ie allowance for wear and abuse which is made 
L the workshop gauges reduces the extent of the 
escribed tolerances, so that work which is within 
e standard limits may sometimes be rejected by 
e workshop gauges. 

Inspection gauges are used to secure that the 
mensions of pieces are such that they can be 
cepted under a contract, and that no work which 
mplies with the specified dimensions is rejected, 
ie tolerances on inspection gauges are, therefore, 
itside the limits of fit specified by the standard 



146 WORKSHOP GAUGES 

tables, and work may be accepted by such 
which exceeds the specified limits by a 
comparable with the tolerances on the gaugi 

For obvious reasons it is most importai 
gauges be measured very accurately, otherv 
advantages and possibilities of a stand 
system of limits and fits cannot be realized, 
inaccurate gauges the tolerance actually g 
the work may be either appreciably greater 
than is intended. The use of such gauges, 1 
lack of means to measure them with si 
accuracy, might result, if the error were 
direction, in the work having to conform 
tolerances than those intended, thus raising i 
of production ; whilst, if the error were 
other direction, the work would have a 
tolerance than that considered desirable, 
prejudice of the resulting fit. The use of slif 
to check limit gauges is illustrated in Figs 41 1 

In the interests of uniformity it may bt 
that the new limits specified by the B.E.S 
be generally adopted, but the Newall systen 
has been employed so widely, is sure to re 
use for some time to come. This need lea 
confusion, for any work machined to the 
limits (see below) ; -will, in general, be wi1 
newB.E.S.A. limits, or so nearly so, that no j 
difficulty will be introduced 

Newall Limits. 

The system of limits for various classei 
developed by the Newall Engineering C< 



LIMITS AND FITS 



147 



hole basis, and the allowances in this system 
.y be summarized as in Table XX 

TABLE XX 

ALLOWANCES FOR VARIOUS CLASSES OF FITS 
(Bom BASIS) 

As laid down by the Newall Engineering Co 

E The minimum diameter of the hole is accurately Its nominal size 
The values for limits and tolerances aro hi ten-thouaarulths of an inch 



mlnal 
meter 
oues 


FOBCB FITS 


DRIVING FITS 


PUSH FITS. 


Limits 


Toler- 
ance 


Llmlta 


Toler- 
ance 


Llmlta 


Toler- 
ance 


Hlfjh 


Low 


High | Low 


High | Low 


ft* . 
to 2 
to 8 
to 4 
to 5 . 
toO . 


+ 10 
+ 20 
+ 40 
+ 60 
+ 80 
+ 100 
+ 120 


+ 5 
+ 15 
+ 30 
+ 45 
+ 60 
+ 80 
+ 100 


5 
6 
10 
IB 
20 
20 
20 


+ 5 
+ 10 
+ 16 
+ 26 
+ 30 
+ 36 
+ 40 


+ 25 
+ 75 
+ 10 
+ 15 
+ 20 
+ 26 
+ 30 


26 
2-5 

5 
10 
10 
10 
10 


-25 
-25 

-26 
-5 
-5 
-6 
-5 


-76 
-75 
-7-5 
-10 
-10 
-10 
-10 


6 
6 
5 
5 
5 
6 
6 



rew Gauges and Limits. 

The questions of screw thread measurement, screw 
uges, and errors in screw threads are too complex 
: any useful discussion to be attempted in the 
ace here available, but the reader who has 
Eistered the contents of this volume will be in a 
isition to study the precise measurement of screw 
reads, and he should undoubtedly undertake this 
teresting and important work. The admirable 
iblications issued by the National Physical 
iboratory will be found most instructive. 



BIBLIOGRAPHY 

THE following publications may usefully be 
consulted by the reader who wishes for furthei 
information on matters related with workshop 
measurements, workshop calculations, and preoisior 
workmanship 

Papers on Mechanical Subjects, by Sir Joseph Whitwortt 

(Spon) 
Mechanical Engineering, by W. J. Lmehain (Chapmar 

& Hall). 
Lockioood's Dictionary of Mechanical Engineering, by J. G 

Homer (Crosby Lockwood) 

Arithmetic for Engineers, by C. B Clapham (Chapman & Hall) 
Metric System for Engineers, by the same author. 
Dictionary of Applied Physics (Glazebrook) Vol. HI, foi 

articles by members of the National Physical Laboratorj 

staff, dealing with screw threads and gauges (Macmillan) 
Notes on Screw Gauges, by the Gauge Testing Stafi of the 

N P L. (H M Stationery Office). 
Gauge Testing Pamphlet, by the N.P.L. Metrology Dept 

{National Physical Lab , Teddington). 
Fine Measurement in Engineering Workshops Reprint oj 

lecture by V I. Norbury Williams (Armstrong, Whitwortl 

& Co.). 
British Engineering Standards Association Reports (B.E.S.A 

28 Victoria Street, S.W.I ; Is. each) 

No 21 Pipe threads for iron or steel pipes or tubes 

No. 27 Limit gauges for running fita. 

No 28 Nuts, bolt heads, and spanners 

No. 46 Keys and keyways. 

No 54 Screw threads, nuts and bolt heads for use ir 
automobile construction. 

No 67 Heads for B.A. screws. 

No. 84 British Association fine screws, threads, anc 
their tolerances. 

No 96 Tables of Corrections to effective diametei 
required to compensate pitch and angle errors in screw 
threads of Whitworth form. 
No 164 Limits and FitB for Engineering. 
C.L. 7270 Interim Beport on British Standard Whitwortfr 

Screw Threads and then* Tolerances. 

148 



BIBLIOGRAPHY 149 

C.L 7271 Interim Report on British Association Screw 
Threads with tolerances for Nos. to 15 B. A. 

5011 1923 Keys, keyways and keybar for shafts up to 
1 Jin. in diameter for automobile parts. 

'he undermentioned Technical Primers,, uniform 
h this volume (Pitman, 2s. 6d. net), are recom- 
ided to those who desire further information 
the subjects specified 

PatternmaJeing, by Ben Shaw and James Edgar. 

Foundrywork, by Ben Shaw and James Edgar. 

Tool and Machine Setting, by Philip Gates. 

Capstan and Automatic Lathes, by Philip Gates 

Grinding Machines and their Use, by Thos. R. Shaw. 

Drop Forging, by Henry Hayes. 

Metallurgy of Iron and Steel, based on the work of Sir Robert 

Hadfield. 

Special Steels, by Thos H Burnham. (Double vol , 5s. net ) 
Industrial Electric Heatong, by J. W. Beauchamp. 
Oils, Pigments, Paints and Varnishe*. by Rupert H. Truelove. 
Small Electnc Motors, by E. T. Pamton 
Industrial Motor Control, by A. T. Dover. 
Belts for Power Transmission, by W. G. Dunkley 
Lubricants and Lubrication, by J. H. Hyde. 

Many other volumes are in preparation for the 
ies of Technical Primers, full particulars of which 
n. be obtained from the publishers at Pitman 
i, Parker Street, Kingsway, W.C.2 



INDEX 



AOY, brochure on, 15 
eats for, 13, 84, 117, 123 
able cahper gauges, 73 
xice, defined, 132 
jan standard thread, 58 

,wire gauge, 63, 06 

ir measurements, 16 

wire gauge, 83, 66 

breads, 57, 68 

A , definition of B.A. 

ad, 58 

, Whitworth thread, 

eporfcs on limits and 
132, 133 

*raphy, 148 \ 
r system, 2, 33 
igham sheet iron gauge, 

are gauge, 63, 65 
and slip gauges, 46, 79 
L & Sharpe, wire gauge, 
66 
'. threads, 67 

KB gauges, adjustable, 73 

, limit type, 72 

rs, care of, 125 
combined, 54, 126 
Brm. joint, 40 
general, 46 
hermaphrodite, 55 
inside, 49, 50, 52, 53, 54, 
126 

keyway, 56 

outside, 49, 50, 52, 63, 
126 

reversible, 54 
screw adjustment, 63, 



Calipers, slide-type, 47 

, special types, 56 

, spring, 61, 65 

, tool-maker's, 52 

, see also slide-calipers, and 

Micrometer calipers 
Care of instruments, 119, 122, 

128 

Collar gauges, 68, 84 
Combination end measuring 

bars, 43 

Combination squares, 111 
Comparison, 11, 12 
Contraction of castings, 35 

DECIMAL division, 2 

, equivalents, 3 

Degrees, 18 
Density, 25, 26 
Depth gauges, 77, 98 
Dial test gauge, 117 
Direct measurements, 11 
Dividers, 54 
Division, 2 

END measuring bars, com- 
bination, 43 

Equivalents, decimals and 
fractions, 3 

, inches and millimetres, 

6,7 

, minutes, seconds and 

decimals of a degree, 20 

, pounds and kilograms, 

23, 24 

, tapers and angles, 19 

FEELER gauges, 67 

Fits, British Standard, 133 

et seq., 140 
, classes of, 129, 143 



151 



152 



INDEX 



Fits, clearance, 140 

- , examples of, 140, 144 

- , gauges, 146 

- , general considerations, 
129 

- , interference, 142 

- , Newall, 146 

- , specifying, 142 

- , transition, 142 

- , see also Limits 
Fractions, 2 

- , decimal equivalents, 3 
Franklm Institute thread, 58 



G rules, 33 
Generation of length standards, 

12 
-- , slip and block 

gauges, 79 

-- , straight edges, 105 
-- , surface plates, 102 
Generator comparator, 13 

HOLE and step gauges, 79 
Hub micrometer, 96 

IMPERIAL wire gauge, 63, 64 
Indirect measurements, 11 
Inspection gauges, 145 
Instrument, selection and care, 

119, 122, 128 
Interchangeability, 131, 133, 

146 

KILOGRAM, standard, 22 

LEAST count, 39 
Limit gauges, 72, 84, 145 
Limits, bases for specifying, 
132 

- , B E S A. Reports, 132, 
133 

- , bilateral system, 132, 133, 
134, 135 

- , British Standard, 133 
ct aeq , 140 

- , gauges, 145 

- , hole basis, 132, 133 



Limits, in repetition manufac 

ure, 131 

, mating surfaces, 135 

, metric, 134 

, Newell, 146 

, non-mating surfaces, 1! 

, oversize holes, 137 

, range factor, 139, 144 

, screw, 147 

, shaft basis, 132 

, size multiplier, 139 

, unilateral system, 13 

133, 134, 135 
Linear measurements, 1, 30 

MASKING off, 102 
Mass units, 18 
Mating surfaces, 135 
Measurements, angular, 16 

, by comparison, 11 

, direct, 1 1 

, indirect, 11, 46 

, linear, 1, 30 

, simple, 27 

Metre, divisions, 11 

, standard, 4 

Micrometer calipers, compe 

sation for wear, 93 

, detachable head, 

, direct reading, 

, general, 85 

, heavy, 94 

Micrometer calipers, how 

read, 87, 90 

, hub, 90 

, inside set, 99 

. , quick adjustme 

device, 92 

, ratchet stop, 92 
sheet metal, 97 
Slocomb, 95 
, special forms, 9fi 
supplementary i 



tings, 91 
Micrometer calipers, " t 

thousandth," 89 
, wear and adju 

ment, 89, 93, 126 



INDEX 



153 



ometer calipers, aee also 
Jipers, and Slide calipers 
ometer depth gauge, 98 
, heads, 09 
, scribing, 98 
ites, 18 

'ALL limit gauges, 74 
.limits, 148 
al band, 15 
-mating surfaces, 135 

BSIZB holes, 137 

ALLAX, 28 

h gauge, 67, 58, 76, 147 

; and ring gauges, 68, 84 

nd, standard, 22 

autions with shrink rules, 

} 

jactors, bevel, 113 

-, draughtsman's, 116 

-, universal, 113 

-, with acute angle attach- 

.ent, 114 

, vernier, 1 14 

ETITION manufacture, 131 

g and plug gauges, 68, 84 

es, 30 

-, British standard, 34 

-, contraction, 36, 36 

-, gear-cutting, 33 

-, graduation of, 31 

-, metric, 34 

-, shrinkage, 36, 36 

es, slide, 43 

-, wear in, 123 

LES, boxwood, 31, 124 

-, ivory, 31, 124 

3W, diameter for drilling, 60 

-, gauges, 147 

-, pitch gauges, 57, 58, 70 

3w, precision gauges, 60, 76, 

47 

-, systems, 57 

ibers, 106 



119 



Scribing blocks, 106 
, micrometer, 98 
Seconds, 18 
Seizure, 130 

Selection of instruments, 
Sellers thread, 58 
Set squares, 110 
Shrinkage of castings, 35 

, tapes, 37 

Slide calipers, 41, 42, 44, 47 

see also Calipers, 



and Micrometer calipers 
Slide rule, 43 

Slip and block gauges, 45, 79 
Slocomb micrometer, 95 
Specific gravity, 25, 26 
Squares, combination, 111 

, set, 110 

Standard caliper gauges, 72 

kilogram, 22 

length, generation of, 12 

metre, 4 

pound, 22 

reference bars, 12, 16, 43 

rules, 34 

screw threads, 57 

sheet iron gauge, 66 

wire gauges, 61-66 

yard, 1 



Step gauges, 79 

Straight edges, general, 110 

, generation of, 105 

Stretch of tapes, 37, 124 
Stubbs, wire gauge 63, 65 
Subdivision of rules, 31 

standards, 13 

Surface, calculation of, 27, 28 

gauge, 107 

plates, 102 

. , angle, 106 

, origination of, 102 

S W G , 63 

TAPER, 16 
Tapes, 36, 124 
Tapping diameter, 60 
Temperature errors, 2 
Test gauge, 117 



154 



INDEX 



Tests for accuracy, 13, 84, 117, 

123 

Thickness gauges, 67 
Thread gauges, 57, 58, 76, 147 

systems, 57 

Tolerance, British Standard for 

holes, 135 

, for shafts, 137 

, defined, 132 

, standard, 133 

Try squares, 1 10 

UNITS, length, 1, 4 

, mass, 18 

, weight, 22 

U S. standard thread, 58 

wire gauge, 63 

VHBNXER, angular, 115 
, how to read, 39, 115 



-, principle of, 38 



Volume, calculation of, 2 
28 

WEAB, compensation for, 9 
125, 126 

- , in rules, 123 
Weight, calculation, 25 

- , units, 22 
Whitworth method of pr 

ducmg surface plates, 102, 
Whitworth threads, 57 
Wickman caliper gauge, 76 
Wire gauges, 61, 63, 127 
Workshop gauges, 146 



, divisions, 2 
, standard, 1 



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>PLANE STRUCTURAL DESIGN T. H. Jones 

d J D. Frier 21 

RAFT AND AUTOMOBILE MATERIALS FERROUS 

W Judge 25 

RAFT AND AUTOMOBILE MATERIALS NON- 

RROUS AND ORGANIC. A. W Judge 25 

CRNATING CURRENT BRIDGE METHODS OF 
.ECTRICAL MEASUREMENT. B. Hague . . 15 

SRNATING-CURRENT CIRCUIT, THE P Kemp 2 6 

IRNATING CURRENT MACHINERY, DESIGN OF 
R Barr and R. D Archibald . . . 30 
SRNATING CURRENT MACHINERY, PAPERS ON 
IE DESIGN OF C. C Hawkins, S P Smith, and 

Neville 21 

3 



s d. 

ALTERNATING-CURRENT WORK. W. Perren Maycock 10 6 
ARCHITECTURAL HYGIENE B F. and H. P Fletcher 10 6 
ARITHMETIC OF ALTERNATING CURRENTS E. H. 

Crapper . . . . . . .46 

ARITHMETIC OF ELECTRICAL ENGINEERING Whit- 
taker's 36 

ARITHMETIC OF TELEGRAPHY AND TELEPHONY 

T E. Herbert and R G de Wardt . . .50 
ARMATURE CONSTRUCTION. H. M. Hobart and 

A G Ellis 25 

ARTIFICIAL SILK AND ITS MANUFACTURE. J. 

Foltzer Translated by S Woodhouse . . 21 
AUTOMOBILE AND AIRCRAFT ENGINES A. W. Judge 30 
AUTOMOBILE IGNITION AND VALVE TIMING, START- 
ING, AND LIGHTING. J B Rathbun . .80 
BAUD&T PRINTING TELEGRAPH SYSTEM H. W. 

Pendry 60 

BLASTING WITH HIGH EXPLOSIVES. W. G. 

Boulton 50 

BLUE PRINTING AND MODERN PLAN COPYING 

B. J Hall 60 

BREWING AND MALTING J Ross Mackenzie . 8 6 
CABINET MAKING, ART AND CRAFT OF. D Denning 7 6 
CALCULUS FOR ENGINEERING STUDENTS. J Stoney 3 6 
CARPENTRY AND JOINERY B F andH. P Fletcher 10 6 
CERAMIC INDUSTRIES POCKET BOOK. A B. Searle 8 6 
CHEMICAL ENGINEERING, INTRODUCTION TO. A. F. 

Allen 10 6 

CHEMISTRY J A FIRST BOOK OF. A Coulthard . 4 6 
COLLIERY ELECTRICAL ENGINEERING. G. M. 

Harvey 15 

COLOUR IN WOVEN DESIGN . A TREATISE ON 

TEXTILE COLOURING. R. Beaumont . . 21 
COMPRESSED AIR POWER A. W. and Z W Daw 21 
CONTINUOUS-CURRENT DYNAMO DESIGN, ELEMEN- 
TARY PRINCIPLES OF H. M Hobart . . 10 6 
CONTINUOUS CURRENT MOTORS AND CONTROL AP- 
PARATUS. W. Perren Maycock . . .76 
COSTING ORGANIZATION FOR ENGINEERS. E. W. 

Workman . . . . . . .36 

DETAIL DESIGN OF MARINE SCREW PROPELLERS. 

D H Jackson 60 

DIRECT CURRENT DYNAMO AND MOTOR FAULTS. 

R. M. Archer 76 



s. d. 

:T CURRENT ELECTRICAL ENG^ELRING J 

Ban . . . . . . . 15 

'T CURRENT ELECTRICAL ENGINEERING, THE 
EMENTS OF. H F. Trewman and G. E. 
difie . . .... 7 6 

ING AND DESIGNING. C. G. Leland . .36 
ING, MANUAL INSTRUCTION. S Baxter . 4 
., BLOUSE, AND COSTUME CLOTHS, DESIGN 
1 FABRIC MANUFACTURE OF. R. Beaumont 42 
MO, How TO MANAGE THE A R. Bottone 2 
MO ITS THEORY, DESIGN, AND MANUFACTURE 



C C Hawkins Vol. I 
ol II 

RIC ARC AND OXY-ACETYLENE WELDING 

L Atkins 



21 
15 

7 6 



RIC BELLS. S. R. Bottone . . .36 
RIC CIRCUIT THEORY AND CALCULATIONS 

Perren Maycock . . . . 10 6 

RIC GUIDES, HAWKINS'. 10 volumes, each 5 
RIC LIGHTING AND POWER DISTRIBUTION 

I. W Perren Maycock . . . . 10 6 

II 10 6 

RIC LIGHTING IN THE HOME L. Gaster . 6 
RIC LIGHTING IN FACTORIES L. Gaster and 
Dow ..... .6 

RIC LIGHT FITTING A TREATISE ON WIRING 

LIGHTING, HEATING, &c. S. C Batstone . 6 
RIC LIGHT FITTING, PRACTICAL F. C. 

sop ... .... 7 6 

RIC MINING MACHINERY S F Walker . 15 
RIC MOTORS AND CONTROL SYSTEMS. A T. 

er . . 15 

RIC MOTORS DIRECT CURRENT H. M. 

art 15 

RIC MOTORS POLYPHASE. H M. Hobart 15 
uc MOTORS, A SMALL BOOK ON. C C. AND 

W. Perren Maycock . . . .60 

uc TRACTION A. T. Dover . . . 21 
uc WIRING, FITTINGS, SWITCHES, AND LAMPS. 

'erren Maycock . . . . . 10 6 
lie WIRING DIAGRAMS W. Perren Maycock 5 

uc WIRING TABLES. W. Perren Maycock . 3 6 



s. d. 

ELECTRICAL ENGINEERS' POCKET BOOK. Whit- 
taker's . 10 6 

ELECTRICAL INSTRUMENT MAKING FOR AMATEURS 

S R Bottone 60 

ELECTRICAL INSTRUMENTS IN THEORY AND PRAC- 
TICE. Murdoch and Oschwald . . . 12 6 
ELECTRICAL MACHINES, PRACTICAL TESTING OF 

L. Oulton and N. J. Wilson . . . .60 
ELECTRICAL TRANSMISSION OF PHOTOGRAPHS M J. 

Martin 60 

ELECTRICITY. R E Neale . . . .30 

ELECTRICITY AND MAGNETISM, FIRST BOOK OF. W 

Perren Maycock . . . . . .60 

ELECTRO MOTORS How MADE AND How USED 

S R Bottone 46 

ELECTRO-PLATERS' HANDBOOK. G. E. Bonney 5 
ELECTRO-TECHNICS, ELEMENTS OF. A. P Young 7 6 
ENGINEER DRAUGHTSMEN'S WORK HINTS TO BE- 
GINNERS IN DRAWING OFFICES . . .26 
ENGINEERING SCIENCE, PRIMER OF E S. Andrews. 

Part 1, 2s 6d ; Part 2, 2s , Complete .36 
ENGINEERING WORKSHOP EXERCISES E Pull . 3 6 
ENGINEERS' AND ERECTORS' POCKET DICTIONARY : 

ENGLISH, GERMAN, DUTCH W. H Steenbeek 2 6 
ENGLISH FOR TECHNICAL STUDENTS. F F. Potter 2 
FIELD MANUAL OF SURVEY METHODS AND OPERA- 
TIONS A. Lovat Higgins . . . . 21 
FIELD WORK FOR SCHOOLS E H Harrison and 

C A Hunter . .... 2 

FILES AND FILING Fremont and Taylor . . 21 
FITTING, PRINCIPLES OF J G Homer . .76 
FIVE FIGURE LOGARITHMS W E Dommett . 1 6 
FLAX CULTURE AND PREPARATION. F. Bradbury 10 6 
FUEL ECONOMY IN STEAM PLANTS A Grounds 5 
FUEL OILS AND THEIR APPLICATIONS. H. V 

Mitchell .... 50 

FUSELAGE DESIGN A W. Judge . 30 

GAS, GASOLINE, AND OIL ENGINES. J. B. Rathbun 8 
GAS ENGINE TROUBLES AND INSTALLATIONS J 

B. Rathbun .... .80 

GAS AND OIL ENGINE OPERATION J. OkiU . 5 



$. a. 
GAS, OIL, AND PETROL ENGINES : INCLUDING 

SUCTION GAS PLANT AND HUMPHREY PUMPS 

A. Garraid 60 

GEOMETRY, THE ELEMENTS OF PRACTICAL PLANE. 

P W Scott 40 

GEOLOGY, ELEMENTARY. A. J. Jukes-Browne . 3 
GRAPHIC STATICS, ELEMENTARY. J. T. Wight . 5 
HANDRAILING FOR GEOMETRICAL STAIRCASES W 

A Scott 26 

HIGH HEAVENS, IN THE. Sir R Ball . .50 
HIGHWAY ENGINEER'S YEAR BOOK H. G Whyatt 6 
HOSIERY MANUFACTURE. W. Davis . . .76 
HYDRAULICS E H LEWITT . . . .86 
ILLUMINANTS AND ILLUMINATING ENGINEERING, 

MODERN. Dow and Gaster . . . . 25 
INDICATOR HANDBOOK. C. N. Pickworth . .76 
INDUCTION COILS G E. Bonney . . .60 
INDUCTION COIL, THEORY OF THE. E. Taylor- Jones 12 6 
INSULATION OF ELECTRIC MACHINES. H. W 

Turner and H, M. Hobart ... 21 

IONIC VALVE, GUIDE TO STUDY OF THE. W D 

Owen 26 

IRONFOUNDING, PRACTICAL J G Homer . . 10 
IRON, STEEL AND METAL TRADES, TABLES FOR THE 

J Steel . . . 36 

KlITBMATOGRAPHY (PROJECTION), GUIDE TO C N 

Bennett . ... 10 6 

LACQUER WORK G Koizumi . . . . 15 
LEATHER WORK C. G. Leland . . .50 
LE^CTRIK LIGHTING CONNECTIONS. W. Perren 

Maycock 10 

LENS WORK FOR AMATEURS. H. Orford . .36 
LIGHTNING CONDUCTORS AND LIGHTNING GUARDS. 

Sir O. Lodge 15 

LOGARITHMS FOR BEGINNERS C. N. Pickworth . 1 6 

MACHINE DRAWING, PREPARATORY COURSE TO 

P. W. Scott 20 

MAGNETISM AND ELECTRICITY, AN INTRODUCTORY 
COURSE OF PRACTICAL. J. R Ashworth 




s d. 
MAGNETO AND ELECTRIC IGNITION. W. 

Hibbert 36 

MANURING LAND, TABLES FOR MEASURING AND. 

J Cullyer 30 

MARINE ENGINEERS, PRACTICAL ADVICE FOR. C 

W.Roberts ... . 5 

MARINE SCREW PROPELLERS. DETAIL DESIGN OF 

D H. Jackson 60 

MATHEMATICAL TABLES W. E Dommett . .46 
MATHEMATICS, MINING (PRELIMINARY). G W 

Stnngfellow. With Answers . . . .20 
MECHANICAL ENGINEERING DETAIL TABLES J P. 

Ross 76 

MECHANICAL ENGINEERS' POCKET BOOK. Whit- 
taker's 12 6 

MECHANICAL STOKING. D Brownlie . .50 

MECHANICAL TABLES . . . .20 

MECHANICS' AND DRAUGHTSMEN'S POCKET BOOK. 

W E Dommett 26 

METAL TURNING J. G. Homer . .40 

METAL WORK, PRACTICAL SHEET AND PLATE E. A. 

Atkins .... ... 7 6 

METAL WORK REPOUSSE C G Leland . .50 
METAL WORK, TEACHER'S HANDBOOK J S Miller 4 
METRIC AND BRITISH SYSTEMS OF WEIGHTS AND 

MEASURES. F. M. Perkin . . . .36 
METRIC CONVERSION TABLES. W E Dommett . 2 6 
MILLING, MODERN E Poll . . .90 

MINERALOGY F. H Hatch . 6 

MINING, MODERN PRACTICE OF COAL Kerr and 

Burns. Part 1, 5/- ; Parts 2, 3 and 4, each . 6 
MINING SCIENCE, JUNIOR COURSE IN. H G Bishop 2 6 
MOTION PICTURE OPERATION, STAGE ELECTRICS, 

ETC H. C Horstmarm and V. H. Tousley . 7 6 
MOTOR TRUCK AND AUTOMOBILE MOTORS AND 

MECHANISM. T H. Russell . . .80 
MOTOR BOATS, HYDROPLANES AND HYDROAERO- 
PLANES. T. H. Russell 80 

Music ENGRAVING AND PRINTING. W. Gamble .21 
NAVAL DICTIONARY, ITALIAN-ENGLISH AND 

ENGLISH-ITALIAN W T. Davis . . 10 6 



5. d. 
)PTICS OF PHOTOGRAPHY AND PHOTOGRAPHIC 

LENSES. J. T. Taylor 40 

'ATENTS FOR INVENTIONS. J. E. Walker and 

R. B Foster 21 

'ATTERN-MAKING, PRINCIPLES or. J. G. Homer 4 
'.PES AND TUBES: THEIR CONSTRUCTION AND 

JOINTING P R. Bjfirling . . .66 

LAN COPYING IN BLACK LINES FOR HOT CLIMATES 

B J.HaU 26 

LYWOOD AND GLUE, MANUFACTURE AND USE OF, 

THE. B C. Boulton . ... 7 6 
'OLYFHASE CURRENTS A Still . . .76 
'OWER STATION EFFICIENCY CONTROL J Bruce. 12 6 
>OWER WIRING DIAGRAMS A T. Dover . 7 6 
'HINTING. H A Maddox 50 

UANTITIES AND QUANTITY TAKING. W. E Davis 6 

RADIO COMMUNICATION, MODERN J. H Reyner 5 
RADIO YEAR BOOK . . . . . .16 

RAILWAY TECHNICAL VOCABULARY. L Serraillicr 7 6 
LEFRACTORIES FOR FURNACES, CRUCIBLES, ETC. 

A. B. Searle ... ..50 

REINFORCED CONCRETE W. N Twelvetreea .21 
REINFORCED CONCRETE BEAMS AND COLUMNS, 

PRACTICAL DESIGN OF. W N Twelvetrees . 7 6 
REINFORCED CONCRETE MEMBERS, SIMPLIFIED 

METHODS OF CALCULATING W. N. Twelvetrees 5 
REINFORCED CONCRETE, DETAIL DESIGN IN. 

E S. Andrews 60 

ROSES AND ROSE GROWING. R G. Kingsley . 7 6 
RUSSIAN WEIGHTS AND MEASURES, TABLES OF. 

Redvers Elder 26 

HOT-GUNS H B C. Pollard . . . .60 
LIDE RULE. A. L. Higgras .... 6 

LIDE RULE. C N. Pickworth . . .36 

OIL. SCIENCE OF THE. C Warrell . . .36 
TEAM TURBINE THEORY AND PRACTICE. W. J. 

Kearton . . . . . . . 15 

TEAM TURBO-ALTERNATOR, THE. L. C. Grant . 15 
TEELS, SPECIAL. T. H. Burnnam. . . .50 

TEEL WORKS ANALYSIS. J. O. Arnold and F. 

Ibbotson 12 6 



5. d. 

STORAGE BATTERY PRACTICE. R Ranlon . .76 
SURVEYING AND SURVEYING INSTRUMENTS. G. A. 

T. Middleton 60 

SURVEYING, TUTORIAL LAND AND MINE T. Bryson 10 6 
TELEGRAPHY : AN EXPOSITION OF THE TELEGRAPH 

SYSTEM OF THE BRITISH POST OFFICE. T. E. 

Herbert 18 

TELEGRAPHY, ELEMENTARY H. W Pendry . 7 6 
TELEPHONE HANDBOOK AND GUIDE TO THE 

TELEPHONIC EXCHANGE, PRACTICAL J Poole 15 
TELEPHONY. T E. Herbert . . . . 18 
TEXTILE CALCULATIONS. G. H. Whitwam . . 25 
TRANSFORMER PRACTICE, THE ESSENTIALS OF. 

E. G. Reed 12 6 

TRIGONOMETRY FOR ENGINEERS, PRIMER OF W. G. 

Dunkley 50 

TURRET LATHE TOOLS, How TO LAY OUT . .60 
UNION TEXTILE FABRICATION R Beaumont .21 
VENTILATION, PUMPING, AND HAULAGE, THE 

MATHEMATICS OF. F Birks . . . .50 
VOLUMETRIC ANALYSIS. J. B Coppock . .36 
WATER MAINS, THE LAY-OUT OF SMALL. H H. 

Hellins 76 

WATERWORKS FOR URBAN AND RURAL DISTRICTS 

H C. Adams 15 

WEAVING FOR BEGINNERS L Hooper . .50 
WEAVING WITH SMALL APPLIANCES THE WEAVING 

BOARD L Hooper ... 76 

WEAVING WITH SMALL APPLIANCES TABLET 

WEAVING. L Hooper .... 76 

WIRELESS FOR THE HOME N. P. Hinton . 1 6 

WIRELESS POCKET BOOK, MARINE W H. Marchant 6 
WIRELESS TELEGRAPHY AND TELEPHONY, An 

INTRODUCTION TO J. A Fleming . .36 

WIRELESS TELEGRAPHY. W H. Marchant . 7 6 
WOOD-BLOCK PRINTING F Morley Fletcher . 8 6 
WOODCARVING C. G Leland . . . .76 
WOODWORK, MANUAL INSTRUCTION. S. Barter . 7 6 
WOOL SUBSTITUTES R. Beaumont . . . 10 6 
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